ADVANCED FORAGE MANAGEMENT - a production guide for coastal British Columbia and the Pacific Northwest 1999

Advanced Forage Management - A production guide for coastal British Columbia and the Pacific Northwest.

Publisher:
Pacific Field Corn Association
P.O. Box 365, Agassiz, BC V0M 1A0
© 1999 Pacific Field Corn Association ISBN: 0-9685015-0-8

Book copies of this publication are sold out.  The individual chapters are available in pdf form in the link below.

About the Publisher:
The Pacific Field Corn Association is a non-profit society registered in BC. Its mandate is to carry out the hybrid evaluation program and to promote research and education related to production of field corn and forage crops in BC. The association membership includes representatives from the dairy and beef industries, Agriculture and Agri-Food Canada, British Columbia Ministry of Agriculture and Food, University of British Columbia (Faculty of Agricultural Sciences), Canadian seed trade, and agri-business.

For information, please write to PFCA, Box 365, Agassiz, BC, V0M 1A0 or contact S. Bittman at tel: 604-796-1735; email: shabtai.bittman@agr.gc.ca

Advanced Forage Management 1999 - PDF's of each chapter

1.  How Grasses Grow

  • The grass plant
  • Germination
  • Leaf growth
  • How does leaf death affect forage production?
  • Stem growth and reproduction
  • Root growth
  • Tiller growth
  • Energetics of growth

2.  Grasses - Good and Bad

  • Perennial grasses - tall
  • Perennial grasses - short
  • Weedy grasses - perennial
  • Weedy grasses - annual
  • How to tell the clovers apart

3.  Nutrient Managment

  • Whole farm perspective
  • Nutrient cycling in forage crops
  • The latest information on nitrogen fertilization
  • Management of nutrients in manure
  • Soil and plant analysis - use a lab or do it yourself
  • Other nutrients and lime
  • Nutrients and feed quality

4.  Weed Management

  • Do weeds affect forage yield?
  • Weeds affect forage quality - and it's not all bad
  • Anti-quality factors
  • Effect of weeds on commercial value of forage
  • Weed lifecycles
  • Strategies for weed management

5.  Grazing Management

  • Pasture growth dynamics
  • Herbage intake - animal factors
  • Herbage intake - forage factors
  • Intensive grazing systems for coastal BC and the PNW
  • Principles of rotational grazing
  • A tale of 4 dairy farms - grazing success stories
  • Ten tips for success
  • The latest stratey for reducing bloat on legume pastures

6.  Rise and Decline of Forage Stands

  • Raising new forage stands
  • Which forages maintain production best?
  • Grasses and white clover
  • Response to irrigation
  • Orchardgrass and tall fescue
  • Decline of forage stands - why it happens

7.  Forage Quality

  • Plant structure
  • Assessing forage quality
  • Forage protein explained
  • Making silage: the fermentation process
  • Absorbents reduce silage effluent
  • Using maturity differences to spread the harvesting season
  • Effect of leaf diseases on nutritional quality of grasses

Chapter 1: How Grasses Grow

The Grass Plant

 

The Growing Point Of Grass Plants Maginfied 300x.

Photo by J.H. Troughton from RHM Langer, 1972. How Grasses Grow. Edward Arnold (Publishers) Ltd. London. 60pp.

Grass plants consist of a collection of shoots called tillers. In the vegetative stage, before flowering begins, the tillers are made of leaf blades and sheaths; what appears to be a stem is really a collection of sheaths and blades rolled or folded one inside the other. The bundle of leaves and sheaths are referred to as pseudo-stems because they resemble stems. The leaves arise in succession from growing points located at the base or crown of the plant (see Fig. 1). The leaves start out as little bumps or nodes on the growing zone. Between these nodes are tiny internode zones, which elongate during the reproductive phase.

Just inside the base of each leaf is a tiny bud that may grow into a new tiller. In bunchgrasses (orchardgrass, perennial ryegrass) the new tiller grows within its leaf. In creeping grasses (quackgrass, Kentucky bluegrass), new tillers grow laterally outward through the leaves.

When the grass becomes reproductive, each of the compressed internodes, located between the leaf nodes, elongate in succession, beginning from the bottom. The resulting elongated internodes become the true stems of the plant. Elongation of the internodes causes the attachment points for all the leaf sheaths or blades to be separated vertically.

Germination

Why good seed-soil contact is important.

The endosperm of seed can suck water from the soil with enormous force, actually a hundred times greater than roots can. Water moves in unsaturated soil either as a liquid or as a vapor; unsaturated liquid flow is slow but vapor flow is much slower. Water can travel only as a vapor across the air gaps around the seed. Hence good contact with firm soil provides most opportunity for liquid water flow.

A grass seed or grain is actually a fruit called a 'caryopsis'. The seed is composed mostly of a large store of carbohydrates, called the endosperm, the embryo which is to become the new plant, and a shield-like structure called the scutellum. Just inside the seed coat is a thin layer of cells called the aleurone layer. After the seed takes up water, these cells produce the enzymes that digest the starch of the endosperm into sugars for the growing embryo. The primary root (radicle) emerges from the embryo, followed by the shoot, called the coleoptile. Annual grasses absorb water and nutrients through the primary roots whereas perennial grasses absorb by secondary roots that emerge from the lowest nodes of each new tiller. When seeds are planted deeper in the soil, a short rhizome-like stem is produced to connect the primary root with the secondary root.

Leaf Growth

 Leaf Growth: consequences for management.

1) During the vegetative phase, growing zones are at the lowest portion of each structure. When fully grown leaves are clipped they cannot resume growth. Leaves with active growth zones that have escaped defoliation will rise above the level of cutting.

2) The tip is the oldest and the base the youngest part of a leaf; hence the tips are first to senesce (die).

3) The lowest leaves tend to escape clipping but these leaves are oldest and least active. These leaves contribute to new growth more by supplying some stored nutrients (sugars, nitrogen, phosphorus, potassium) than by producing new sugars.

4) Nitrates are converted to protein in the bases of leaves, consuming much of the energy captured by the rest of the leaf.

One of the secrets for success of grasses as forages is that leaf growth continues during and after defoliation, until flowering begins. This is possible because the growth zone is at the bottom end of the leaves and sheaths thus remaining close to the soil surface during vegetative growth. Hence, if some of these growth zones are removed, they can be readily replaced with new tillers. No other plant family is so well designed to recover from defoliation.

At the very base of each tiller is the tiny region of growth called the 'apical dome' (see Fig. 1). New leaves initiate in succession on opposite sides of the apical dome. Leaf initiation is a continuous process so that at any time there is a series of new leaves at various stages of development. Just inside each new leaf is a bud that can potentially develop into a new tiller.

 

 The Growing Point Of Grass Plants Maginfied 300x.

Photo by J.H. Troughton from RHM Langer, 1972. How Grasses Grow. Edward Arnold (Publishers) Ltd. London. 60pp.

The growing zone for leaves is actually made up of two parts, the upper producing the leaves and the lower producing the sheaths. As the sheath grows, it raises the leaf until the growth zone at the bottom emerges from the bundle of older sheaths. When the bottom of the leaf, including the ligule, is exposed, leaf cells no longer divide and the leaf is fully formed. The sheath continues to grow after the leaf has stopped. Meanwhile, the next leaf is already moving up. For most grasses, no more than three leaves are growing at one time. Once a leaf is fully formed, its main function is photosynthesis and production of protein.

Growth rate of grasses is determined by rates of leaf initiation and leaf growth. Leaf initiation of our temperate grasses is influenced by temperature (best at 20-24°C for perennial ryegrass and slightly higher for orchardgrass.) Nutrients (especially nitrogen) and water are needed to make the new leaves grow.

How Does Leaf Death Affect Forage Production?

Soon after a leaf is fully expanded, its photosynthetic activity gradually declines. About one-third of the food energy produced is shuttled to young leaves, tillers and roots. Aging leaves at the bottom of the sward do not contribute much food energy, but some of their soluble nutrients are eventually shifted to new plant growth.

The longevity of grass leaves is lower than many broadleaf plants. Leaf death is hastened by deficiency of water and nutrients (especially nitrogen and sulphur) and especially by shading. The rate of leaf appearance is generally balanced with leaf death, so that the number of live leaves on a tiller is rather consistent and usually less than five. Recent studies have shown that productivity of grasses is often under-estimated because the contribution of dying leaves is neglected.

Stem Growth and Reproduction

Bunching or creeping grasses?

Bunchgrasses are usually more productive than creeping grasses because they do not invest in underground stems that cannot be harvested. As plant numbers decline, bunchgrass swards are subject to invasion by weeds, including some creeping and non-creeping grasses. Some farmers use seed mixtures that include creeping grasses to forestall invasion. Tall fescue is a popular choice because it is not aggressive and has good agronomic features. However, maintaining a balanced sward with several species is more challenging than maintaining pure stands. Aggressively creeping grasses such as creeping foxtail and smooth bromegrass can become weed pests.

One of the secrets for success of grasses as forages is that leaf growth continues during and after defoliation, until flowering begins. This is possible because the growth zone is at the bottom end of the leaves and sheaths thus remaining close to the soil surface during vegetative growth. Hence, if some of these growth zones are removed, they can be readily replaced with new tillers. No other plant family is so well designed to recover from defoliation.

At the very base of each tiller is the tiny region of growth called the 'apical dome' (see Fig. 1). New leaves initiate in succession on opposite sides of the apical dome. Leaf initiation is a continuous process so that at any time there is a series of new leaves at various stages of development. Just inside each new leaf is a bud that can potentially develop into a new tiller.

The Growing Point Of Grass Plants Maginfied 300x.

Photo by J.H. Troughton from RHM Langer, 1972. How Grasses Grow. Edward Arnold (Publishers) Ltd. London. 60pp

The growing zone for leaves is actually made up of two parts, the upper producing the leaves and the lower producing the sheaths. As the sheath grows, it raises the leaf until the growth zone at the bottom emerges from the bundle of older sheaths. When the bottom of the leaf, including the ligule, is exposed, leaf cells no longer divide and the leaf is fully formed. The sheath continues to grow after the leaf has stopped. Meanwhile, the next leaf is already moving up. For most grasses, no more than three leaves are growing at one time. Once a leaf is fully formed, its main function is photosynthesis and production of protein.

Growth rate of grasses is determined by rates of leaf initiation and leaf growth. Leaf initiation of our temperate grasses is influenced by temperature (best at 20-24°C for perennial ryegrass and slightly higher for orchardgrass.) Nutrients (especially nitrogen) and water are needed to make the new leaves grow.

Root Growth

Grasses have two root systems. In annual grasses, only the first roots that emerge from the seed absorb nutrients and water. In perennial grasses, the primary roots are active for a few months and then die off. After that, the roots that form at the stem bases take over, but they also generally last only one year.

The root system is continuously ‘turning over’ as old tillers die and new ones are formed. Low soil temperature, poor shoot growth and frequent defoliation reduce root growth (see Chapter 5, Fig. 1). The turnover of grass roots contributes greatly to nutrient cycling and build-up of soil organic matter. Some temperate grasses produce as much or more growth below than above the ground.

Tiller Growth

Number and size of tillers determine yield of grasses. Tall species, such as orchardgrass, timothy and bromegrass, harvested for conservation, can produce high yields with comparatively few tillers because each tiller can be large. Short, pasture-type grasses, such as perennial ryegrass, bluegrass and fine-leafed fescues, must produce many tillers to attain high yield. Under grazing management, grasses are usually kept short so tiller density is very important.

A new tiller arises from the bud located just inside the leaf base that surrounds it. The tiller emerges from the encircling leaf sheath in one of two ways. In ‘bunch’ grasses (timothy, orchardgrass, perennial ryegrass) the tiller grows upwards within the sheath and emerges near the base of the parent leaf. Each new tiller may also give rise to other tillers called secondary tillers, and so on. In ‘creeping grasses’ (reed canarygrass, Kentucky bluegrass, quackgrass), the tiller breaks through the protecting sheath and gives rise to a lateral stem called a stolon (when on the soil surface) or rhizome (below the ground surface). The creeping grasses can also form ‘bunch’ type tillers.

During vegetative growth, every leaf supports a bud that can potentially develop into a new tiller. The number of tillers that actually form depends first on genetics. For example, timothy tends to produce fewer tillers than perennial ryegrass. Indeed, new varieties of perennial ryegrass are selected for tiller abundance. But environmental factors may be more important than genetics for regulating tiller number, probably through the action of the anti-aging hormone called cytokinin. As with leaf growth, tiller numbers are affected by mineral nutrition (especially nitrogen), water status and light levels, but tiller initiation may also be influenced by colour of light falling on the crown.

Tiller formation usually ceases during the reproductive phase (beginning with stem elongation), probably due to hormonal suppression by the stem apex. This means that when grasses are most likely to be cut (boot stage), they have relatively few new tillers. Orchardgrass maintains more active tiller buds than other grasses and tall fescue usually has many elongated tillers that escape cutting.

Energetics Of Growth

Grasses store food as a sugar-like molecule (fructosan), not so much in roots (they’re too skinny) as in the crown and fleshy stem bases (or rhizomes). Timothy and some wild grasses have a storage organ called the haplicorm. The haplicorm can be felt as a swelling just below the ground (see Chapter 2).

Plants use carbohydrate reserves stored in stem bases, crown and roots to support new regrowth after cutting. Grasses feed on these reserves for 2 - 7 days after harvesting to produce enough new leaf surface to provide for new growth. Harvesting grasses at the boot stage offers the best compromise between yield and quality but, because food reserves and new tillers are in low supply at this stage, recovery growth is delayed. Orchardgrass, perennial ryegrass and tall fescue are better adapted to harvesting at this stage than timothy and bromegrasses.

Chapter 2: Grasses - Good & Bad

Perennial Grasses - Tall

Orchardgrass

Tips For Identifying

-Orchardgrass can be distinguished by its very compressed (flat) leaf sheaths (like barnyardgrass-see below) but with a short to medium-length ligule.

-Colour varies from gray to lime green according to variety.

Forage Facts

-True bunchgrass, does not spread.
-Very high yield, excellent all-around grass.
-Withstands harvesting or grazing at all growth stages because it conserves food reserves during stem elongation.
-Varieties range in maturity by up to 3 weeks.
-Competitive with weeds and clover, especially the early maturing varieties.
-Good summer growth, even without irrigation.

Downside
-Does not tolerate flooding for long periods.
-Susceptible to stripe rust and virus; stands rarely last more than 3-4 years.

Tall fescue

Tips For Identifying

-Tall fescue can be identified by its stubby auricles and these auricles generally have short hairs (in contrast to meadow fescue).

-Leaves are shiny and smooth on bottom surface and grooved on top, moderately wide (over 5 mm or 3/16 in). Leaves feel rough, particularly on leaf edges, but some new varieties have softer leaves.

-Can be confused with meadow fescue (which has no hair on auricle) and Italian ryegrass (which has reddish stem bases).

Forage Facts

-Classified as a bunchgrass but spreads due to lateral growth of lower stem.
-Closely related to ryegrass; can be hybridized with annual ryegrass producing intermediate types called 'festulolium'.
-Produces a strong sod.
-Relatively low growth habit and open canopy make it suitable for grazing and compatible with white clover (reports of strong competition from clover in some areas).
-Usually persistent, tolerates heat, drought, and alkalinity; also performs well under wet conditions. Very winterhardy.
-Dries rapidly after cutting.
-Grows late in fall.

Downside

-Seedlings grow sluggishly so establishment is challenging.
-May have lower palatability than orchardgrass.

Meadow fescue

Tips For Identifying

-Meadow fescue resembles tall fescue but meadow fescue has narrower leaves and no short hair on auricle; also ligule is very short.

-Meadow fescue also resembles Italian ryegrass; meadow fescue has a shorter ligule, and rough edges on leaf blades.

-Bunchgrass.

Forage Facts

-Not widely grown in region but more winter hardy than tall fescue.
-Hybridized with ryegrass to produce 'festulolium' varieties.

Downside

-Poor productivity in this region.

Timothy

Tips For Identifying

-Timothy can be distinguished from other cultivated grasses by the swelling at the base of the stem, just below soil surface (feel by pushing finger about 1 cm or 1/2 in into soil); the swelling is a fleshy storage organ called 'haplicorm'.

-Other identifying features are its rather long (more than 2-3 mm, 1/16 in) and pointed ligule, usually with a notch on either side; also no auricles or hair on collar.

Forage Facts

-True bunchgrass.
-Very persistent, winter hardy, and high yielding.
-Can be used to produce forage for horse industry but otherwise does not excel primary grasses.
-Later maturing than other grasses.
-Tolerates some flooding.

Downside

-Very small seed must be seeded very shallow, but seedlings are reasonably vigorous.
-Weakened by harvesting or grazing during stem elongation, like bromegrasses.

Italian ryegrass

Tips For Identifying

-Italian ryegrass can be identified by its broad leaves, with shiny bottoms and rough upper surfaces, similar to tall fescue. It can be distinguished from tall and meadow fescue by its reddish stem bases and smooth leaf edges, rather longer ligule and narrower auricles.

-Italian ryegrass can be distinguished from perennial ryegrass by its wider leaves which are rolled, not folded, when they emerge.

Forage Facts

-True bunchgrass.
-Longevity ranges from true annuals (Westerwold varieties) to short-lived perennials that live 3 or more years.
-Most rapid establishment of forage grasses and seed can emerge from more than 3 cm (1.2 in) depth in good soils.
-Highest nutritional quality and palatability except for perennial ryegrass.
-Conditioning of stock to ryegrasses may be desirable because of high alkaloid levels.
-Moderate flooding tolerance.
-Can be inter-cropped with corn.

Downside

-Marginal winter hardiness.

Reed canarygrass

Tips For Identifying

-Reed canarygrass can be distinguished by its extremely broad hairless leaves (10-18 mm, 3/8 to 11/16 in) and its great height (2 m or 7 ft).

-Ligules relatively short compared to size of leaf and tip of ligule may be turned back.

Forage Facts

-Spreads by creeping rhizomes.
-Tolerates flooding better than any other cultivated grass.

Downside

-Small, oily, usually expensive seeds that have a short shelf-life.
-Has not persisted well in trials at PARC (Agassiz).
-Coarse grass considered to be unpalatable for pasture due to alkaloids. New varieties have reduced alkaloid levels.
-Seedlings are very sluggish hence difficult to establish.

Bromegrasses (smooth, meadow, sweet, prairiegrass)

Tips For Identifying

-The bromegrasses can be distinguished from other cultivated grasses because their sheath collars, where leaves are attached, are closed (like a 'V-neck' pullover) unlike other grasses where sheath is split and often overlapping all the way down (like a cardigan).

-Growth habit ranges from aggressively creeping (smooth bromegrass) to slowly creeping (meadow bromegrass) to true bunchgrasses (Pacific, prairiegrass, sweet and the weedy downy bromegrass).

Forage Facts

-Smooth bromegrass has perhaps most aggressive rhizomes of cultivated cool-season grasses.
-Meadow bromegrass is probably the best suited of the bromegrasses for forage production, but is somewhat inferior to the commonly used grasses in this region.
-Smooth bromegrass and sweet bromegrass have not proven well adapted for forage production in the region.
-Prairiegrass is reputed to have excellent nutritional quality but few detailed tests have been done locally; prairiegrass has very low winter dormancy and very early spring growth; it is potentially high yielding but is generally insufficiently hardy or persistent; very large seed but has only moderate vigour.

Downside

-Most bromegrasses are weakened by defoliation during the period of stem elongation because root reserves are low, hence bromegrasses are generally not well suited to grazing; meadow bromegrass is an exception.

Perennial Grasses - Short

Perennial ryegrass

Tips For Identifying

-Perennial ryegrass can be recognized by its narrow leaves (2-6 mm, 1/16 to 1/4 in) with distinctly grooved upper surface and very glossy and smooth lower surfaces.

-Perennial ryegrass can be distinguished from annual ryegrass because its leaves emerge folded, not rolled, from the sheath.

-Perennial ryegrass sometimes resembles Kentucky bluegrass but ryegrass leaves have grooved upper surface and do not have prow-shaped leaf tips.

-Note that seed heads of perennial ryegrass are slender spikes that resemble quackgrass except that seed clusters (florets) are attached edgewise instead of flat along the stem.

Forage Facts

-Bunchgrass.
-Shortest of major cultivated grasses; productive stands must contain a lot of tillers.
-The most palatable and digestible forage grass available.
-High content of soluble carbohydrates helps it ensile.
-Varieties have wide range of maturity (up to 4 weeks).
-Well adapted to heavy soils that are wet in spring.
-Excellent for grazing, need to encourage abundant tillers.
-Performs best near the coast because it does not like summer heat or drought and is moderately susceptible to cold.

Downside

-Slow to wilt and dry.
-Stands usually last only 3 years.
-Poor drought resistance and marginal winter hardiness.

Kentucky bluegrass

Tips For Identifying

-Kentucky bluegrass can be identified by these features: leaf tip that looks like a boat prow when held sideways; translucent lines that can often be seen along the mid-rib when leaf is illuminated from behind; emerging leaves that are folded, not rolled; both leaf surfaces are smooth.

Forage Facts

-Spreads by rhizomes.
-Although rarely seeded as a forage, it is an important pasture grass because it frequently volunteers.
-Persists in pastures because it is extremely winter hardy and grazing tolerant.
-'Apomictic' reproduction, which means it produces seeds asexually, hence is actually clone of mother plant.
-Very wide geographic distribution.
-Resembles other bluegrass species such as Canada bluegrass and fowl meadowgrass.

Downside

-Because it is so persistent, bluegrass gradually pushes out more productive forage species in pastures and hayfields.

Fine fescues

Tips For Identifying

-The fine fescues have very narrow leaves which fold when dry, with deep ridges on upper surface.

Forage Facts

Very tolerant of grazing and cold.

Sheep fescue/ hard fescue

Tips For Identifying

-Bunchgrasses

Forage Facts

-These grasses are suitable for use as ground cover between rows for nursery and berry crops.

 

Creeping red fescue

Tips For Identifying

-Sod-former.

-Ligule is very short (longer on sides than back) and leaves are very narrow with ridged upper surface.

Forage Facts

-Encroaches on dry pastures if seed source is present.
-Used in lawns because it survives and retains colour even under prolonged dry conditions.

Bentgrasses

Tips For Identifying

-Bentgrasses are most easily identified by their inflorescence. Unlike most cultivated grasses, each seed on the panicle is solitary, not in a group of 2 or more. Leaves are flat and sheaths are rolled.

Brown top

Tips For Identifying

-Very short ligule.

Forage Facts

-Invader in poor pastures, indicator of poor production.

 

Red top

Tips For Identifying

-Very long ligule (up to 6 mm or 1/4 in).

Forage Facts

-Grows in moist areas and has high yield potential but may be relatively unpalatable.

Turf-type timothy

Tips For Identifying

-Very slow growing and winter hardy hence makes an excellent ground cover. Soft leaves are easy to mow.

Weedy Grasses - Perennial

Quackgrass or couch grass

Tips For Identifying

-Quackgrass can be identified by long (2 mm or 1/16 in) thin auricles, short ligule, usually hairy stem bases, and very distinct rhizomes.

Downside

-Probably most important grassy weed in Canada.

Velvetgrass or Yorkshire fog

Tips For Identifying

-Velvetgrass is easily recognized by velvety hair all over sheath and leaf.

-Stems and leaves are very pale green.

 

 

Downside

-Probably most important grassy weed in Canada.
-Spreads by above-ground prostrate stems called stolons.
-Common weed in old forage fields.
-Related species (Holcus mollis) has rhizomes.

Pacific bromegrass

Tips For Identifying

-Pacific bromegrass has a v-collar like other bromegrasses but its leaves and sheaths are usually very hairy and its ligules are very long with hair on back.

-Native perennial bunchgrass.

Meadow foxtail

Tips For Identifying

-Meadow foxtail resembles timothy superficially, because of a similar spike-like seed head. Unlike timothy, meadow foxtail heads emerge very early in spring (late April); also, its seeds are very soft and fluffy, and it has a shorter ligule without notches.

-Meadow foxtail is very noticeable in spring because it is first grass to head out, otherwise goes unnoticed.

Forage Facts

-Bunchgrass.
-Occasionally used as a forage in northern Alberta because of early growth, grazing tolerance and flooding tolerance.

Downside

-Can become a weed because of early seed formation.
-Sown in pasture in northern Alberta but nutritional quality has been called into question in northern BC trials.

Weedy Grasses - Annual

Barnyard grass

Tips For Identifying

-Barnyard grass can be easily identified even when very small by its very flat (or compressed) and hairless sheath, very smooth (hairless) leaves, and absolutely no ligule.

Downside

-Barnyard grass is a bunchgrass that can grow 2 m (6 ft) tall amongst tall crops like corn or be short and prostrate when mowed, in both cases producing persistent seed.
-Summer annual weed that germinates in warm soils in May-Aug.
-Grows very rapidly in hot weather.
-Major weed in corn and can be a problem in newly seeded grass stands.

Crabgrass

Tips For Identifying

-Crabgrass leaves have several stiff hairs (over 1 mm or 1/16 in) in or near the collar region.

Downside

-This weed seems to be gaining a foothold in the region.

Green and yellow foxtails

Tips For Identifying

-The foxtails are most easily recognized by their ligule, which is a fringe of hair, and scattered hair on leaf sheath and upper leaf blade.

-Green foxtail has a fringe of hair on edge of sheath while yellow foxtail has long soft hair at the base of the leaf blade.

Downside

-Bunchgrasses.
-Warm season grassy weeds that germinate and grow after mid-May.

Annual bluegrass

Tips For Identifying

-Annual bluegrass has leaves with prow-shaped tips, as other bluegrasses, but the leaves are much shorter.

Downside

-Very short-lived winter or spring annual bunchgrass.

-Can seriously interfere with new seedings.
-Does not compete with well-established forages except in high traffic areas.
-Flowers at any time of year; very prolific seed producer.

Annual bromegrass

(cheatgrass or downy bromegrass and soft chess)

Tips For Identifying

-The annual brome weeds have v-necked collars, as other bromegrasses, but their leaves and stems are very hairy and their ligule is very short.

Downside

-Mostly germinate in late fall or early spring under cool moist conditions.

How To Tell The Clovers Apart

White clover

-White to slightly pink flowers.
-Leaves and stems not hairy.
-Growth is prostrate with stem growing along the ground and rooting at nodes.
-Leaves usually have watermark.
-Leaf stipules small.
-'Ladino'clover is 3-5 times bigger than white clover but otherwise similar.

 
 
Alsike clover

 

-White to pink flowers.
-Leaves and stems not hairy.
-Upright growth habit.
-Leaves have very large stipule and generally no watermark.
-Veins in leaflets appear to extend beyond leaf margins.

 
 
 
Red clover

 

 

-Pink to purple flowers.
-Leaves and stems are hairy.
-Upright growth habit.
-Leaves have a watermark.

Chapter 3: Weed Management

Do Weeds Affect Forage Yield?

Weeds tend to fill gaps in forage stands. Hence, eliminating these weeds might result in no immediate yield increase and could actually diminish forage yield. It can be assumed that most weeds produce less herbage than adapted forage crops. If weeds were as productive they, might in themselves be planted as the forage. Indeed, scientists have discovered that aggressive and vigorous grassy weeds like quackgrass and barnyardgrass have surprisingly low yield potential compared to the forages that they compete with.

 

Fig 1. Dandelion poised to expand into space made available by decline of diseased orchard grass. (See Chapter 6)

Weeds are successful because they are particularly adapted to invade, spread and reproduce. Most weeds have evolved to prolifically produce seeds and rhizomes but this is at the expense of useful herbage. Once they are established in gaps, weeds are poised to exploit any weakness in the crop. Forage crops have been developed for high yield and disease resistance, but some weeds are better adapted than forages to tolerate grazing and clipping, injury by pests, diseases or environmental stresses such as cold, drought, soil compaction, treading, and so on. As these environmental and biological stresses weaken the forage, adapted weeds expand their occupation (Fig. 1). Quack-grass contains allelopathic substances (natural plant toxins) that can inhibit the growth of adjacent tame forage plants. This property assists quackgrass in gradually dominating a forage stand.

In a study on a stand of orchardgrass with 10 - 20% dandelion, manually eliminating the weed increased forage yield by only 7%. In this example the use of 2,4-D for dandelion control would likely result in some economic benefit. However, the greatest benefit of controlling encroaching weeds may be delaying the decline of the host forage crop that the weeds would otherwise help to bring about. Because weed-forage interactions are complex, we have little information on economic threshholds (weed population at which economic gain from controlling weeds offsets the cost of the control measure) for control of weeds in forage crops.

       
 Fig 2. Perennial sowthistle.  Fig 3. Lamb's quarters.  Fig 4. Curled dock.  Fig 5. Lady's thumb.
     
Fig 8. Barnyard grass.
 
Fig 9. Shepherd's purse.
 Fig 6. Wild mustard.  Fig 7. Tansy ragwort    
     Fig 10. Corn spurry.  Fig 11. Broadleaved dock.
       

Weeds Affect Forage Quality - And It's Not All Bad

Weeds As Environmental Indicators

Weeds in crops are as often the result of a problem as the cause of it. Weeds readily find spaces caused by such environmental factors as poor drainage, inadequate fertility, high or low pH, soil compaction, disease and insect attack, and poor harvesting and grazing practices. Encroachment by dandelions indicates weakening of the forages by factors such as winter injury, disease and insects. Buttercups and bog rush (slough grass) prefer wet soils, hence are indicative of poor drainage. Bracken grows best under acid soil conditions while foxtail barley prefers high pH soils. Perennial bluegrass species and bentgrasses indicate overgrazing, and annual bluegrass appears on compacted soils. Horsetail often indicates light, dry soils with coarse texture and low organic matter.

Weeds may lower or improve the nutritional quality of a forage stand. Several annual weeds (such as redroot pigweed and lamb's quarters) and perennial weeds (including dandelion, Canada thistle and perennial sow-thistle) have nutritional quality equivalent to alfalfa when harvested at the same time. When these weeds are harvested along with the forage crop, they may improve the feeding quality of the silage. Research in Saskatchewan has shown that broadleaf weeds have a better balance of copper and molybdenum than either cultivated or volunteer grass species on pasture, so cattle are less likely to experience copper deficiency on weedy pastures.

First-harvest dandelions that are in bloom typically contain about 3 percentage points less protein than orchard-grass, but dandelions that are mostly in a vegetative stage in later harvests have similar protein content to that of orchardgrass. In feeding trials, dandelions often equal orchardgrass in palatability, either in pasture or as properly cured hay. The overall digestibility and the digestibility of the plant protein (see Ch. 7) are similar in dandelions and alfalfa.

Quackgrass, like dandelions, has reasonably good nutritional value. While quackgrass is maligned as a weed, the grass is used as a parent in grass breeding programs for its nutritive value and palatability. Protein content and palatability of quackgrass and timothy are similar according to some reports in the literature. Other studies have shown that quackgrass has 3 percentage points less crude protein content than orchardgrass at the flowering stage.

In contrast, other common weeds such as shepherd's-purse, curled dock, smartweed (lady's thumb) and foxtail are usually lower in nutritive value than forage grasses and therefore undesirable as a feed component.

Anti-Quality Factors

Weeds often introduce undesirable nutritional factors that must be considered:

Excess moisture: Dandelions contain up to 7% more moisture than alfalfa and require at least an extra day to dry before baling. To make matters worse, weeds usually form compacted swaths and tedding often shatters their leaves resulting in losses. Hay comprised of a considerable amount of dandelion or other large-leafed weeds often turns black and moulds.

Tainting flavour of milk: Many weeds in the mustard family such as stinkweed and wild mustard contain anti-quality factors that can taint milk flavour.

Nitrates: At some growth stages and under specific growing conditions weeds such as redroot pigweed, lamb's quarters, Canada thistle, barnyardgrass and smartweed can contain toxic levels of nitrates.

Toxins: Some of the common poisonous weeds found in Coastal forages include tansy ragwort, buttercup, bracken fern and field horsetail. None of these weeds should be grazed or fed to livestock in large quantity.

Effect Of Weeds On Commercial Value Of Forage

If the forage is sold, discounts of about 1% for each percentage of weeds are often imposed on weedy hay, up to a weed percentage of 20 - 25%. Hay containing more than 20 - 25% weeds is usually not marketable. Concern about the nutritional quality of the weeds may be a factor in the rejection of forage. Therefore, when the forage is destined for sale, the use of herbicides may be justified at relatively low levels of weed infestation.

In fields that are badly infested with weeds, herbicide applications will likely not result in production of sufficient additional tame forage to compensate for the weeds that were removed. Furthermore, new weeds may re-invade the new openings. Therefore, these fields should probably be removed, at least temporarily, from commercial hay production.

Weed Lifecycles

An understanding of the way weeds grow helps in planning management to control their growth and possible spread. Weeds fall into four categories based on their growth habits: summer annual, winter annual, biennial and perennial.

Annual weeds

Some annual weeds grow best in warm temperatures while others prefer cooler conditions. Summer annual weeds complete their entire growth cycle, from germination to seed formation, in one growing season. Common examples of summer annual weeds are redroot pigweed, lamb's quarters, annual smartweed, barnyardgrass, and yellow or green foxtail. Many of the summer annual weeds grow best in very hot temperatures and tolerate drought remarkably well, thanks to a specialized physiology (called C-4 metabolism) not enjoyed by any of our perennial forages. These weeds do not germinate until mid-May, so seeding in early spring or fall is the best and cheapest way to avoid these nasty pests.

Winter annual weeds germinate in the cooler and moister conditions of late summer or fall and typically produce a rosette of leaves in the fall. Examples include shepherd's purse, annual bluegrass and corn spurry. In our coastal climate, these plants may continue to grow through much of the winter and then surge in the early spring and complete their lifecycle well before summer. Many of the weeds that behave as winter annuals may also germinate in early spring, long before the summer annuals.

Annual weeds do most damage to new forage stands but also invade established stands damaged by pests or harsh winters. The firm, fine and nutrient-rich seedbed prepared for small-seeded forages is equally well-suited for germination and establishment of weeds. Well-established and vigorous forage stands fend off invading annual weeds and, over time, help to reduce populations of weed seeds in the ground. Thus, growing forages after several years of corn reduces the weed load.

Table 1. Seed production and dormacy of some common weeds.
Weed # of seeds produced per plant # of years that seed may remain viable in soil
Canada Thistle 630/stem 11-20
Chickweed 10
Dandelion 15,000
Curled Dock 29,500 80+
Barnyardgrass 7,160
Green Foxtail (millet) 34,000
Lamb's Quarters 72,450 21-40
Redroot Pigweed 129,000 21-40
Lady's Thumb 19,000
Shepherd's Purse 33,500 35
Tansy Ragwort 150,000

Biennial and perennial weeds

Biennial weeds germinate one season and complete their growth cycle by shedding seed in the following year (e.g. common burdock, bull thistle, wild carrot). Perennial weeds live for more than two years, by definition, and some may live almost indefinitely. Perennial weeds often found in forage crops, such as quackgrass, velvetgrass, bluegrass, curled dock and Canada thistle are very difficult to control. These weeds increase as the stand ages, until eventually renovation is required. Growing corn for a year or two after grass helps reduce the load of perennial weeds from the field.

Weed Seeds

Important to consider in making a weed control decision is the weeds' reproductive potential. Most weeds are successful as a result of perennial root survival, high seed production, and long-term seed dormancy and viability. Understanding these aspects can help answer the question "If I don't control it now will it continue to spread and increase my management costs?

Strategies For Weed Management

The Manure Connection

Be aware that many weed seeds remain viable after storage in silage or hay and passing through the animal. In fact, the passage through the animal's digestive tract may actually induce dormant weed seeds to break their dormancy and germinate. Thus, weedseed-containing manure applied to fields will continue the weed growth cycle (See Table 2).

Seed stored in solid manure for 4-5 months, or heat-composted (60 C or 140 F) for 3 weeks will lose viability hence breaking the weed-animal-manure application cycle.

1. General

-Start with a clean field where perennial weeds have been controlled.

-Use high-quality clean seed and species that are well-suited to your area and soil conditions. Note that certified seed has very low allowable levels of weed seeds, especially those classified as primary noxious weeds. -Use establishment techniques that favour the forages and not the weeds. This includes early planting, good seedbed preparation, and uniform shallow seeding, with greatest attention to forages that are slow to establish. -Once established, vigorously growing forages will keep out most weeds. It is difficult for weeds to get started in a dense, well-managed grass or grass/legume stand.

2. Weed control before seedbed preparation

It is best to control perennial weeds before seeding takes place. Perennials such as quackgrass, curled dock or Canada thistle are very difficult to control once they are established in grass or legume stands. Also, root pieces from many of these plants can be spread by cultivation equipment when the seedbed is being prepared. Many of these root pieces will produce new plants very rapidly.

If perennial weeds are present in the field you are planning to seed, the most successful control is usually obtained by applying the herbicide glyphosate (Roundup®, Touchdown®, and Victor®). Glyphosate is sprayed onto the perennial weeds before the field is cultivated. In spring, the perennial weeds must have at least 20 cm (8 in) of active growth before they are sprayed.

Late fall application usually gives excellent control with glyphosate because the plants are moving carbohydrates into the crowns and the herbicide will be carried along to the crown and roots where it will produce the greatest effect. Another advantage of fall application is that the sod will be killed and begin to break down over winter. This saves time and produces a better seedbed in spring.

Complete control of perennial weeds, especially dandelions, will not be accomplished with a single herbicide application. Additional herbicide or tillage operations will likely be required before complete control of perennial weed species is achieved.

Table 2. Viability of weed seeds after passing through various classes of livestock
Weed Name Horses Cattle Swine Sheep
Canada Thistle No Yes Yes
Chickweed Yes Yes Yes Yes
Curly dock Yes Yes Yes Yes
Dandelion No No Yes Yes
Green Foxtail Yes Yes Yes Yes
Smartweed Yes No
Lamb's Quarters Yes Yes Yes Yes
Quackgrass Yes Yes No No
Tall Buttercup Yes Yes Yes Yes

Can perennial weeds be controlled by tillage alone? The strategy is to repeat tillage frequently, whenever root pieces begin to regrow, until all the food reserves are depleted. Success using tillage will depend on the type of perennials being controlled, how much root reserve they have, growing conditions and the amount of time available to utilize this technique. The technique works best under good growing conditions. If the soil is very dry, the root pieces will become dormant so tillage will have little effect.

3. Control of weeds during seeding and establishment

Seedling forages do not compete well against the many species of annual weeds that germinate at the same time as the forage. Weeds are much easier to control when they are seedlings, before they have suppressed the forage stand. Species with sluggish seedlings (e.g. tall fescue, reed canary-grass, timothy) are the most susceptible to weed competition whereas those with very vigorous seedlings (notably the ryegrasses) need much less weed management.

Table 3. Seedling vigour affects amount of weed infestation in new stands of perennial forages.
Type Weed Content
Perennial ryegrass 30%
Orchardgrass 30%
Mix (Orchard + ryegrass) 39%

A. NURSE (COMPANION ) CROPS (SEE CH.6)

Cereal companion or nurse crops can be used to compete against weeds and reduce likelihood that a herbicide will be needed (Table 4). The cereal nurse crops should be planted at half the usual seeding rate, about 40 - 50 kg/ha (35 - 45 lb/ac), at the same time as the forage. At higher seeding rates, the cereals will themselves compete too much with the forage. It is most important to harvest the nurse crop early, not later than the soft dough stage, to release the forage seedlings from competition for light and water. Companion crops allowed to grow tall might be lodged (knocked over) by wind or rain, smothering the forage seedlings underneath. Research at PARC (Agassiz) showed that use of a nurse crop made it unnecessary to apply herbicides when establishing either perennial ryegrass, orchardgrass or a mixture of the two.

A variation on companion cropping used by some farmers is to seed a short-lived vigorous grass (such as Italian or perennial ryegrass) with the slower establishing, more persistent orchardgrass or tall fescue. The persistent grasses are expected to eventually take over the sward, while the short-lived grasses prevent weed encroachment. The key to success appears to be balancing the seed populations to ensure that the ryegrasses are not overwhelming. While the ryegrasses are less competitive than cereals initially, they remain adversaries for a much longer time.

Table 4. Companion crops reduce weeds in newly seeded grass crops at PARC (Agassiz) in 1986-1988.
Establishment Method Weed Conent

Initial Harvest

No weed control 65%
Herbicide 41%
Barley companion crop 22%
Oats companion crop 24%

B. CLIPPING AND GRAZING

Timely clipping or grazing is commonly used to reduce competition and production of new seeds by annual weeds. Clipping or grazing when the stand is very young can cause wheel and hoof damage including rutting, poaching and compaction of fields that are still soft. Left too long before clipping or grazing, forage seedlings will be suppressed. Excessive weed competition and new weed seeds will be produced. Most annual weeds will not regrow after clipping because their growing points are removed but there are exceptions, such as barnyardgrass, which will regrow and continue to produce seed even if cut very close to the ground. The forage seedlings do regrow quickly after weeds are clipped. Clipping encourages the grasses to produce more tillers, making the sod more dense and competitive.

It is important to remove the excessive clippings from the field in some way. This will prevent smothering of the young forages and remove any weed seeds from the field. Forage stands are often clipped with flail harvesters that put the forage and weeds into a wagon. The harvester should have very sharp knives to minimize damage to the small forage plants. Speed of recovery is faster with clean cuts made by sharp knives. The collected herbage will consist mainly of weeds. Before feeding the weeds, consider impact of the weeds on forage quality (see Pg. 54).

C. HERBICIDES

Herbicides can control many broadleaved weeds during establishment but few herbicides are available for controlling grassy weeds. Inexpensive herbicides for broadleaved weed control, such as MCPA amine 500, are effective when used correctly. A common reason for failure is late application. Best control is achieved when the weeds are at the 2 to 4-leaf stage. Note that most grassy annual weeds are heat-loving and do not germinate until May. Planting forages in April or earlier will minimize the effect of the pernicious annual grassy weeds.

4. Weed control in established forages

Good forage management is essential to prevent encroachment by weeds. A well-established, properly fertilized forage crop will exclude weeds. If grassy weeds become a problem, it is almost impossible to get rid of them without completely renovating the stand. Fine-leafed grasses (bluegrass and bentgrass - see chapter 3) will fill in areas where the forage has been killed out by compaction, traffic and overgrazing. These weedy grasses are usually unproductive.

In many cases, broadleaved weeds in established forages can be controlled with a herbicide. The herbicide used will depend on the grass and legume species, how the crop is being used and which broadleaved weeds are present. Proper weed identification is essential so you can select the right herbicide. It is important to find out grazing or cropping restrictions that apply for the herbicide you are going to use. For example, if you plan to treat curled dock plants with Banvel 480 at the recommended rate of 2.0 L/ha (26 oz/ac), you must wait at least 7 days before allowing dairy cattle to graze the treated field.

Chapter contributed by Michael Betts and Roy Cranston (BCMAF) and Jim Moyer (Agriculture and Agri-Food Canada, Lethbridge Research Centre).

Chapter 4: Grazing Management

Pasture Growth Dynamics

Forage produced on well-managed pasture is one of the most cost-effective feeds that can be produced and utilized in British Columbia and the Pacific Northwest. When properly managed, grazed forage is of higher feed value than any form of conserved forage because harvesting is frequent and there are no storage or harvesting losses. A good understanding of how grasses grow is very helpful in managing pastures effectively (See Ch. 1).

Herbage growth rates are very high in spring, and because the pastures have not yet been grazed, height of herbage is fairly uniform across all the grazing land. For pastures consisting mainly of taller forages, such as orchardgrass, tall fescue, red clover and alfalfa, the optimum height for grazing is typically 20 - 25 cm (8 - 10 in). In contrast, optimum height is 10 - 15 cm (4 - 6 in) for low growing species such as perennial ryegrass, fine-leafed fescue, bluegrasses, bentgrasses and white clover. Carefully managed strip grazing can be used to effectively graze tall herbage.

Surprisingly, over 40% of seasonal production occurs before the end of May in our region. Because of the rapid growth in spring, first grazing should begin early; for tall species when forage heights reach 10 - 12 cm (4 - 5 in), for short species at about 7 cm (3 in). Grazing of tall species should be stopped at 4 cm (1.5 in) and the grazing of short species should be stopped at 2.5 cm (1 in).

Starting grazing of some of the pasture land at this intensity helps create a staggered forage regrowth pattern and promotes tillering and new leaf development. This strategy 'conditions' the forages to maintain leafy, high-quality herbage over a longer period of time.

Another pasturing strategy to help maintain a constant supply of high-quality feed is to use a compliment of early and late-maturing varieties. The late-maturing varieties will maintain feed quality later into the growing season than early-maturing varieties.

Table 1. Effects of clipping intensity on tillers, roots and leaves of grass plants.

Number of Tillers Weights of Plants at End Of Test
Treatment At Start
Of Test
At End
Of Test
Roots
(grams)
Leaves
(grams)
Not clipped 87 431 147 202
Clipped to 12.5 cm 77 427 78 160
Clipped to 7.5 cm 81 192 30 59
Clipped to 3.8 cm 73 53 7 18

Grazing and Animal Health

When I was a student 20 years ago, my professor of dairy nutrition, Dr. Grieves, taught us about a phenomenon in dairy cattle called "Dry Lot Depression". He described that cattle continuously in confinement and dry lot conditions would not perform as well as cattle that were pastured for a few months every year. The reasons given were rather vague and the poor performance was not well defined at the time.

In today's intensive dairy operations, farmers must maximize animal density to ensure profitability. On some farms, this has had grave effects upon animal comfort, health, disease, and psychological stress-for both farmers and their cows.

Dairy cows do not live as long today as in the past. Farmers are often compelled to cull otherwise good cows because of lameness, injury, or reproductive problems. Sound grazing practices could help us manage our dairy animals so that they remain productive longer meaning fewer replacement heifers would be needed. Also, higher herd production averages may be attained since a dairy cow would reach peak production in her fifth or sixth lactation.

Many dairy cows are culled because of reproductive failure and unobserved heats are the biggest reason for reproductive culls. Grazing systems allow cows to socialize more naturally and with less competition. This allows sexually active groups to form around cows that are in and around heat. One study showed that cows would stand to be mounted six to eight times an hour on pasture versus just two mounts an hour on a slippery barn floor.

Infectious diseases thrive on psychological stress and crowding. Pasturing can help reduce infectious diseases by simply dispersing the animals and reducing close contact. Calving pens can be emptied and given a thorough cleaning while cows are allowed to calve on pasture.

 

 Fig 2. Grazing makes cows smile!

Exercise is a forgotten element in intensive animal production systems. Young rapidly growing animals develop stronger feet and legs if allowed to roam freely. Mature cows have fewer post calving problems. In fact, cows with feet and leg problems or physical injuries from comfort stalls will usually rejuvenate after a period on pasture. No one has developed a so-called 'comfort stall' that is as comfortable as a field of soft grass!

Despite the many health benefits, it is important to be alert to potential problems associated with grazing and animal health. The following are ten potential health problems to look for on pasture:

1. Internal and external parasites
2. Plant and chemical poisoning
3. Bloat
4. Grass tetany
5. Nutrient (macro and micro) deficiency or imbalance
6. Rapid changes in pasture nutritional quality
7. Heat stress
8. Poor water availability
9. Lameness due to rocky lane ways
10. Mastitis due to mud holes and sloughs.

If you anticipate and remedy potential health problems on pasture, the health benefits of grazing far outweigh the problems. Grazing makes cows smile!!

Contributed by E. Reynolds, D.V.M., Little Mountain Veterinary Clinic Ltd., Chilliwack BC.

Herbage Intake - Animal Factors

Fig 3. The goal of grazing management is to maximize intake.

The daily growth of the herbage determines the maximum number of animals that can be stocked per hectare of pasture. However, daily intake of nutrients ultimately determines the productivity of animals in any livestock operation. Likewise, herbage intake is the overall factor that governs animal productivity on pasture.

The goal of grazing management is to maximize intake.

Grazing behaviour

Feed consumption (intake) depends on the following factors:
- Grazing Time: How long does the animal spend grazing?
- Bite Rate: How rapidly does the animal take bites?
- Bite Size: How much forage does the animal consume per bite?

Daily Intake = Grazing Time X Bite Rate X Bite Size

Of these three factors, bite size seems to affect the intake rate most. When herbage is in short supply bite size is small so animals try to compensate by increasing both their biting rate and grazing time. When this happens, usually intake is diminished.

Bite weight depends on the amount and distribution of herbage offered within the pasture. The bite size is determined as:

Bite Volume X Density of the selected herbage

The bite volume is the product of bite area and bite depth. Both bite depth and consequently bite volume increase as sward height increases. If the herbage is very dense, livestock will take smaller bites.

To manage your pastures for maximum rate of herbage intake, consider the following factors:

Physical attributes of animals

Intake of concentrates by animals in confinement is primarily regulated by their energy requirements. In contrast, intake of forage is limited also by the animal's physical ability to accommodate the bulky herbage material. Therefore, large animals with low body condition (skinny) and large reticulo-rumen capacity (big stomachs) can accommodate more herbage, hence are inclined to have high intake rates.

Physiological condition of animals

Physiological status of the animals also influences consumption. For both cows and ewes, forage intake

A. increases slightly over maintenance levels during mid-gestation
B. declines in late pregnancy (in spite of increasing energy needs)
C. drops off sharply around parturition
D. rebounds during lactation.

During early lactation, forage intake lags behind energy requirements, so body reserves are utilized. Late in lactation, intake remains high, while milk production drops off, so body reserves are replenished. Lactating cows consume 35 - 50% more forage than gestating cows of the same weight and on the same diet, under conditions of high feed availability.

Intake is also regulated by the rate at which the forage is digested and passes through the rumen, which is affected by quality. Low-quality forages, which are slowly digested due to high fibre content, are retained in the rumen longer. When ingesting low quality forage, the animal feels full quickly and ceases to graze. In contrast, highly digestible, immature forages are slightly laxative, which means they pass quickly through the rumen enabling the animal to graze and ingest more.

The Mechanics of Grazing:

How cattle, sheep and horses eat on pasture

Grazing is a complex activity. It starts with the search for and selection of suitable herbage. After selection, the animal prehends (grasps) the herbage and takes it into its mouth. The forage is then chewed, mixed with saliva, formed into a bolus, and forcefully swallowed down into the forward part of the rumen. Varying amounts of time are spent on each activity. Jaw activity during grazing is complex and differs for each livestock species because each animal has a unique arrangement of jaw, teeth, and other mouth parts.

CATTLE grazing tall herbage use their tongues to encircle the herbage and draw it into the mouth. Short grass is gripped between the upper and lower molars or between the incisor teeth in the lower jaw and the muscular pad of the upper jaw, then severed by a backward jerk of the head. The horizontal movement of the grazing animal's head results in a mower effect, with the tops of the plant being "trimmed" off evenly. Cattle do not graze closer than 5 cm (2 in) from the ground unless forage is in short supply.

SHEEP either bite the foliage off the plant or break it off by gripping the herbage and jerking their heads backward or, less commonly, forward. Sheep are similar to cattle in having only a muscular pad in the upper jaw rather than teeth. In contrast with cattle, sheep have a cleft upper lip that permits close grazing.

HORSES have both upper and lower sets of incisors. These teeth enable horses to bite closer to the ground than sheep and cattle.

All three species move with their muzzles in a horizontal plane as they graze and select forage in a vertical plane. Because sheep have the smallest mouths, they can take small bites and so are able to be most selective of plant species and plant parts. However, all three species are able to vary their methods of harvesting forage according to the structure of the vegetation.

 
Fig 6. Changes in duration and frequency of grazing bouts each day over the growing season.

Diurnal grazing pattern - can it be manipulated to increase intake?

Grazing lactating dairy cows typically have about five meals per day. Each meal lasts an average of 110 minutes (Fig. 5). The first meal of the day begins shortly after dawn, followed by two to three meals between morning and afternoon milking. A long and intensive meal around dusk (8 PM) provides sufficient food to digest during the night period. A short meal (30 min) may be taken at about 1 AM but the rest of the night is spent ruminating and resting. Cattle with lower intake requirements in relation to their weight (e.g. dry cows, mature bulls) have fewer and shorter meals.

While cattle feed mainly between dawn and dusk, night-time feeding will take place when intake requirements are high or days are short. Cattle spread out their meals over the daylight hours by manipulating length and number of meals, hence in mid-summer there are a greater number of meals in the daylight but they are of shorter duration (Fig. 6). Nocturnal feeding is more likely to occur on a well-lit night, and in hot, humid conditions night grazing is in creased to limit exposure to sun during the day.

Table 2. Daily activities of horses, cattle, and sheep on pasture.
Horses Cattle Sheep
Average time in hours spent on activity*

Values in parentheses represent the range

Grazing 14

(10.8 - 16)

9

(5.4 - 12.7)

9

(8.4 - 10.6)

Standing 8

(5.6 - 10.1)

4

(1.1 - 9.4)

3

(1.1 - 6.6)

Lying Down 1

(0 - 1.6)

9

(8.5 - 11.3)

11

(8.3 - 13.1)

The speed of grazing or biting is reduced at night, probably because the cattle do not have the necessary visual cues for fast herbage selection. As the day progresses, both the proportion of time spent grazing and the rate of biting increase. This increased rate of herbage intake is due also to an increase in sugar content of the herbage over the day and the need to store up sufficient food for digestion at night.

Can an understanding of these daily and seasonal grazing habits be used to manipulate the grazing system for increased intake? Possibly. If cattle have their biggest meal at dusk, they should be out on pasture at that time and not in the barn being milked. Furthermore, cattle should have an ample supply of fresh herbage for their large dusk meal.

How Horses Graze

Horses have a different grazing behaviour than ruminants. Whereas cattle can be managed to graze a pasture quite uniformly, horses like to pick their spots. They designate certain areas for feeding ("lawns" or "greens") and other areas for defecation ("roughs"). Close attention to management of horse pastures is critical because if left to their own habits, horses will overgraze the greens, potentially weakening the stand.

Weather and Grazing

The climate along the west coast of North America is well suited for grazing because of moderate temperatures. Intense heat reduces feed intake on pasture, but the jury is still out on what is the best way to deal with it. Providing shade makes cattle more comfortable but won't necessarily increase feed intake because when the animals are standing under a tree, they're not eating! If the livestock are kept on pasture without shade, they must be provided with ample water at all times.

Cold wet weather is a significant factor for those farmers near the coast who are able to graze in the winter season on well-drained land.

Herbage Intake - Forage Factors

Table 3. Quantity of available herbage affects intake.
Available herbage kg/ha (lb/ac) of dry matter Intake % Of

Maximum

2200-3600

(2000-3200)

100
1800 (1600) 97
1350 (1200) 93
900 (800) 83
450 (400) 60
225 (200) 35

Improving animal productivity by maximizing forage intake is a function of the quantity and quality of the herbage consumed by the animal. Which affects intake most: quantity or quality of forages?

Digestibility and protein content of grazed herbage is usually higher than that of conserved feed. This is because the herbage on pastures is generally younger, storage losses have not occurred and animals can select their feed. Intensive grazing systems typically maintain sufficiently high forage quality to meet the dietary requirements expected from the forage component of the diet. However, even high-quality pasture herbage may limit the quantity of forage consumed when the supply is inadequate. For this reason, quantity of available forage more often limits animal production on pasture than forage quality.

 
Fig 8. Relationship between intake and organic matter (ash removed) digestibility for temperate grasses.

To ensure maximum intake, livestock must be provided with herbage of sufficient volume (height and density). This holds as long as growth stage is not so advanced that quality rather than supply limits intake. Canopy height and density affect bite size by the grazing animal.

Maximum feed intake takes place when there is 2200 - 3600 kg/ha (1 - 1.5 T/ac) dry matter of standing herbage. For tall grasses like orchardgrass, optimum initial grazing height is between 20 and 25 cm (8 - 10 in). For short grasses, like perennial ryegrass, optimum initial grazing height is 10 - 15 cm (4 - 6 in) in dense stands and 15 - 20 cm (6 - 8 in) in thinner stands. Optimum height for grazing tall fescue is in between. Sufficient grass should always be available so as not to limit intake, even during the last hours of grazing a field.

Table 3 shows how intake declines when there is inadequate herbage mass. Given the importance of available herbage to intake, several devices have been developed to help farmers estimate the standing herbage on their pastures. These devices range in complexity from calibrated walking sticks and falling plate meters to sophisticated electronic capacitance meters.

Our cool-season grasses are best suited for grazing while they are in the vegetative growth stage because at that time they consist of only leaves and sheaths and have no true stems (see Chapter 1). Ruminants select young, green leaf tissue and avoid stems and dead material. Of the cool- season grasses, orchardgrass and tall fescue flower only in spring and remain mostly vegetative throughout summer and fall. Timothy and some varieties of perennial ryegrass flower more than once in a growing season.

Grazing And Dung Patches

An advantage of grazing is that animals return nutrients, in the form of dung and urine, back to the ground. Grazing should be managed so that livestock distribute dung and urine uniformly over the paddock. Uniform grazing minimizes the need for supplemental nutrients.

Animals soon graze over urine patches but avoid dung patches for a much longer period of time. The area avoided can be several times larger than the actual dung deposit. Pasture losses due to fouling of the grass may range from 45% under low stocking rates to below 10% under high stocking rates. Under high stocking rates, competition for feed forces animals to graze close to the dung deposit.

Encouraging uniform grazing over the entire paddock helps to evenly distribute dung and urine, and reduce pasture losses due to avoidance. This is best accomplished by keeping stocking rates high and residency periods short. For high-producing dairy cattle, the residency period should be no more than a day. Some producers chain harrow paddocks after grazing to break up dung patches or clip the rejected stalks but both practices are probably of questionable benefit. Under local high rainfall conditions, intensively managed cows fully graze "dung areas" within 2-3 grazing rotations (less than 2 months).

Table 4. Comparision of 'Management Intensive Grazing' to 'Traditional Grazing' techniques.
Characteristic Managment Intensive
Grazing
Traditional Rotational
Grazing
Stocking Density * Up to 200 cows/ha
(80 cows/ac)
5 - 20 cows/ha
2-8 cows/ac)
Stocking duration 12-24 hours 1-2 weeks
Rotation length 10-20 days 30 days +

Concentrate supplementation and water supply affect intake on pasture

In situations where nitrogen is limiting, the addition of small amounts (

Keeping an adequate water supply within a relatively short distance ensures herbage intake is not limited due to water shortage and walking time. As long as cattle have to walk less than 250 m (820 ft) to water, grazing patterns and subsequent defecation patterns will be uniform throughout the pasture. Forage located beyond this distance from a water source will be under-utilized. It is important to note that if the cattle establish a particular grazing pattern during early grazing cycles, the effect becomes much greater later in the season. Forage rejected early at far distances from water becomes more mature and is even more likely to be rejected later in the season.

Perennial Ryegrass for Pastures in the Pacific Northwest

Perennial ryegrass is among the most palatable of all forage grasses, meaning that animals seem to prefer it to other grasses. Perennial ryegrass also produces the highest sward density of any pasture grass, helping grazing animals to achieve the maximum dry matter intake (See Herbage Intake - Forage factors). Most importantly, perennial ryegrass (and closely related Italian ryegrass) is highly digestible so that it has a very high energy (TDN) content (see Ch.7). High digestibility means fast rumen passage, leading in turn to yet more feed intake. Dry matter intake is the key to high milk production, high average daily gain, and overall high animal performance.

The combination of palatability, density, and digestibility is the reason that farmers in New Zealand, Western Europe and the UK depend on perennial ryegrass almost exclusively for grazing and conserved feed. However, many farmers are concerned that perennial ryegrass is insufficiently hardy for colder-than-average winters in the Pacific Northwest.

Many of the perennial ryegrass varieties first introduced to North America originated in New Zealand. Varieties from New Zealand remain active during winter rather than becoming dormant. Experience has shown that to survive winters here, perennial grasses must have more winter dormancy than found in New Zealand varieties. The climate in European countries like Holland is much more like ours. Crops in Holland are often exposed to winter temperatures reaching -15 degrees C (0 degrees F) without protection from snow cover. Many of the new perennial ryegrass varieties from Europe become dormant in the fall and have considerably more winter hardiness than in the past. This means that farmers will be able to plant more ryegrass pastures without losing sleep.

Contributed by J. Thijssen, Barenbrug, USA and S. Wallace, Mid West Forage Sales

Intensive Grazing Systems For Coastal B.C. And The PNW

Fig 10. Tumble-wheel type electric fence facilitiates controlled grazing.

Many graziers in coastal BC and the Pacific Northwest use the high intensity/short duration grazing system. The reported advantages are:

- Animals spread out quickly so grazing and defecation are uniform over the paddock.
- Stand persistence may be greater because individual plants are grazed only once during a grazing period. - Selectivity is reduced so even less-preferred species are grazed and thus maintained in optimal growth condition.
- Trampling is minimized and pastures have ample time for rest and recovery.

It should be pointed out that research in New Zealand and the United Kingdom has not shown that high intensity /short duration grazing systems produce more grass, promote better utilization, or improve animal production compared to continuous grazing. In these countries, rotational grazing is practised only to ration feed in the fall or whenever herbage is in short supply.

How well does the experience overseas apply here? Unfortunately, we have little experimental data. We do know that there are some differences in our situation. Many farmers here graze orchardgrass and tall fescue rather than perennial ryegrass, which is by far the dominant grazing grass in both New Zealand and the UK. Orchardgrass and tall fescue should be allowed to attain a greater height than perennial ryegrasses at the start of grazing and the taller herbage is better grazed with intensively managed systems. Furthermore, land is scarcer and nutrient supplements are more heavily used in our region. Finally, expectations for milk production on both 'per cow' and 'per land area' bases are far greater in our region than in New Zealand or the UK due to economic differences. These factors suggest that controlled grazing systems may indeed be well suited for some farms in coastal regions of BC and the Pacific Northwest

Principles Of Rotational Grazing

(Also referred to as Prescribed Grazing Management or Management Intensive Grazing)

The goal of rotational grazing management is to allow plants to continually produce large volumes of high quality leaf material by setting (1) frequency, (2) intensity and timing, and (3) duration of grazing.

Frequency of Grazing

The period of time a pasture is allowed to recover between successive grazings is referred to as the rest period. The rest period (plus residency time, see below) sets the frequency with which a pasture is grazed. Rest periods should vary over the growing season to allow plants to achieve their maximum rates of growth without becoming so tall and rank that quality is reduced and intake losses occur (see Fig. 8). Note that maximum growth rate occurs at a greater height with tall grasses (orchardgrass) than short grasses (perennial ryegrass, bluegrass).

During the spring, orchardgrass and tall fescue pastures of coastal BC and the PNW produce 100-125 kg/ha (90-110 lb/ac) of dry matter per day. In a 15 - 20 day growth period, the forage height will reach 20 - 25 cm (8 - 10 in) and contain between 1200 and 2000 kg/ha (1100 - 1800 lb/ac) of dry matter available for grazing above a 5 cm (2 in) residual stubble height. During the summer and early fall, growth rates slow to 50 - 70% of those in the spring so a longer rest period (25 - 30 days) is required to accumulate a similar amount of forage. Long rest periods occasionally expose forages to the risk of leaf diseases such as as scald (late spring and summer), stripe rust and powdery mildew (late summer and fall).

Table 4. Comparision of 'Management Intensive Grazing' to 'Traditional Grazing' techniques.
Characteristic Managment Intensive
Grazing
Traditional Rotational
Grazing
Stocking Density * Up to 200 cows/ha
(80 cows/ac)
5 - 20 cows/ha
2-8 cows/ac)
Stocking duration 12-24 hours 1-2 weeks
Rotation length 10-20 days 30 days +

Intensity and Timing of Grazing

The degree to which pasture herbage is grazed down during a grazing event is referred to as the intensity of grazing. The greater the intensity of grazing, the greater the rate of forage utilization, and the greater the harvest efficiency. In practice, grazing intensities are evaluated by comparing pre-grazing and post-grazing forage heights.

When establishing grazing heights, the most important factors include (1) type of pasture plants, (2) time of year, and (3) production objectives of the livestock enterprise.

Pastures consisting of tall grasses (timothy, orchardgrass, tall fescue, reed canarygrass) and legumes (red, ladino and alsike clover, etc.) should be grazed from an initial forage height of 20 - 25 cm (8 - 10 in) down to a residual stubble height of 5 - 6 cm (2 - 2.5 in). This results in 70 - 80% apparent forage utilization. However, the time of year must also be taken into consideration.

Fig 11. The duration that livestock are allowed to access a paddock or field is called the residency period.

On wet soil conditions, where punching or poaching (excessive trampling) of the pasture could be a problem, it is best to let the forage accumulate to a greater height prior to grazing and then to leave a larger proportion of the forage in the pasture after grazing. Keep in mind that grazing cattle may uproot tall grasses on wet soils. Orchardgrass is probably more susceptible to being uprooted than tall fescue or perennial ryegrass. Although this method will help protect the soil and the stand, it does reduce harvesting efficiency, and will require that the pasture be clipped once the soil dries out.

Grazing heights may also need to be adjusted during hot dry weather. Some producers say that it is best to leave more residual forage in the pasture to shield the soil from the sun in order to prevent excessive soil temperatures and encourage good root growth. A large proportion of roots are near the soil surface and leaving some forage canopy protects the roots from overheating and drying out.

Fig 12. Cattle graze selectively; they consume the best forage first and leave the rest for last.

Choice of grazing height has a different effect on productivity per animal and productivity per unit of land area. As the proportion of herbage utilization increases, production as measured on an individual animal basis decreases. This is because the longer and more closely livestock graze a pasture, the amount and quality of forage available for grazing declines. As a result, there is a reduction in dry matter intake per animal and in individual animal performance.

In contrast, increasing the amount of forage utilization increases production per unit area. Even though production per animal is lower, a greater number of animals may be supported, and as a result, a greater amount of the forage produced is converted into livestock product. Paradoxically, if too much of the available forage is utilized, not only is there a reduction in production per animal, there is also a reduction in the amount of production per area.

Farmers must find a compromise between maximizing production per animal and per land area that suits the production objectives of their livestock enterprise. Because grazing heights are the primary controlling factor in the efficiency of pasture production and utilization, they can be extremely useful in guiding the compromise. For optimum animal performance, the previously recommended residual forage heights would be increased by perhaps 50%. For maximum production per land area, residual forage heights should be reduced by perhaps 25%. Managing grazing heights is a skill gained with grazing experience.

Duration of Grazing

The duration that livestock are allowed access to a paddock or field is called the residency period. Residency periods are based on balancing the total amount of forage required by the livestock with the amount of forage in the pasture so that an appropriate amount of forage utilization is achieved. Note that for continuous grazing, residency time is season-long.

The principle of rotational grazing is that residency periods should be long enough to allow the stock to harvest the forage, but not so long that damage to plant growth occurs from uncontrolled defoliation. Residency periods should also ensure that livestock performance is not reduced below acceptable limits, and that forage is not wasted through increased trampling and fouling with manure and urine. When forage supply is in balance with demand, selecting a shorter residency period will provide a higher and more consistent quality of forage, and increase forage consumption by grazing animals (improved harvest efficiency).

Animals graze selectively, they consume the highest quality forage first and leave the rest for last. Unfortunately, what is left is subjected to increased amounts of trampling and fouling with manure and urine. As a result, the longer the grazing animals reside in a paddock, the greater selection they will exercise. Extending residency periods for too long not only reduces the amount of forage actually harvested, it can also negatively influence animal performance.

In order to maintain high and consistent levels of milk production, lactating dairy cows should be given fresh paddocks every milking or every other milking (Table 5). Other classes of livestock can meet their minimum nutritional requirements with longer residency periods (including season-long occupancy - called continuous grazing) provided the total forage supply is adequate, and wasting forage is not a concern. However, where maximizing forage production and harvest efficiency are indicated as primary concerns, residency periods should not exceed seven days.

Manure Lagoon liquid is applied with irrigation water. Blended 1:6 with irrigation water. Have flush barn with solid/liquid separator. Cattle will graze right under the gun. Solids applied on silage/hay field. Apply 3.5 million L (900,000 US gal) of manure over entire acreage. 2 applications. Use Nova meter when applying to know nutrient content. In general, 150,000 L (40,000 US gal) contains 20kg (50 LB) of ammonium-nitrogen. Irrigate with lagoon water on pastures 3 times during growing season: late February, mid-June, August. Solid manure goes on neighbour's land.
Lime Very important. Lime is used to supply calcium more than to adjust pH. Yes, over 100 tons/year applied on farm. Yes. pH values have been ammended with lime. Over the last 8 years have raised pH from 5 to 5.6 Yes, lime is applied at 600-1200 kg/ha (500 to 1000 LB/ac) every 2nd year.
Pasture harvesting On first crop, will harvest some pastures for silage when grass gets ahead. Will make silage out of lowland pastures for 1st crop. Upland pastures only clipped if growth exceeds consumption. Will harvest pastures as silage when grass gets ahead. Close-off field sections of 4-8 ha (10-20 ac) and harvest as silage or hay. Generally, no more than once a year. Usually set aside 6 ha (15 ac) for silage. The key is harvesting early.
Fencing Main paddocks have a permanent single-strand electric fence. Secondary paddocks are larger, about 4 ha (10 ac) and subdivided as necessary with temporary electric fence. Permanent electric fence around larger paddocks, up to 12 ha (30 ac), subdivided with temporary electric fense. Use 'tumblewheel' fences in front of herd, and ploy wire reel in back of grazing herd. Perimeter fencing is a combination of high tensile wire and barbed wire. Permanent electric fence around large paddocks, 4-6 ha (10-15 ac), subdivided with temporary electric fence.
Weed management (see Chapter 5) Not a big deal - clip thistles. We let the cows do it. Spot-spray thistles. Clip weeds once during the season. In the more acid soils, buttercup can be a concern. Most weeds, except for bull thistle, are palatable and nutritious. Cows will eat Canadian thistle if mowed and prickles are facing away.
Main advice Attitude. Attitude - make up your own mind what you're going to do and do it! Farms ask me about switch to grazing to save their operations. If they are heavily capitalized (buildings and equipment), a switch to grazing can't save them. Intensive grazing can provide more satisifying management option for many farmers. Intensive grazing managment takes about an 80% time commitment in labor (just like confined operations), but you're outside more with your herd and that makes it worthwhile. The cows are working for their feed, instead of the farmer. Need to be flexible in all your

Ten Tips For Success

Farmers' recommendations for successful grazing

1. Do your homework. Read up on the latest information on grazing management. Get a firm grip on how grasses grow (see Ch. 1).

2. "PLAN, PLAN, & REPLAN" - Develop a written Grazing Management Plan starting with a list of objectives. Make sure the plan takes into account the soil, plant and climatic characteristics specific to your operation.

3. Design and construct a cost-efficient fencing system that will keep the cattle in and be easy to manage.

Dry laneways are essential for effective grazing management. 

4. Design and construct a solid laneway that won't turn into mud when the rains come.

5. Establish a watering system that ensures cattle have a ready supply of fresh water. They shouldn't have to walk all the way to the barn to get it.

6. Monitor fields regularly to ensure consumption and production of forages are in balance. Walk each paddock at least every 10 days making careful observations. Make sure that the plants are always in a growing state.

7. Be flexible. If cows can't keep up with forage production, set aside some land to harvest as conserved forage. If forage production is getting behind, don't overgraze. Provide livestock with supplemental feed.

8. Once you are convinced grazing is for you, plant grass varieties bred particularly for grazing. Legume/grass mixes help reduce nitrogen requirements, but beware of bloat (see 'Latest strategies for reducing bloat,' on p. 71).

9. Develop an irrigation system to ensure consistent growth in dry years and through the drier months of summer.

10. Develop a nutrient management strategy that makes best use of manure and minimizes fertilizer costs. The strategy should outline how you will apply manure without smothering or fouling the foliage.

The Latest Strategy For Reducing Bloat On Legume Pastures

What is bloat?

Cattle grazing on pastures with a high content of legumes may be killed by a digestive disorder called 'frothy bloat'. In North America, this condition is primarily encountered on pastures containing white clover and alfalfa. Frothy bloat occurs when the eructation (belching) mechanism is impaired by frothy, foamy rumen content. Gas produced naturally in the rumen remains trapped in the rumen fluid, forming an emulsion of small bubbles about 1 mm (1/25 in) in diameter. The frothy material expands and fills the rumen. As the rumen fills, the nerve endings that control the opening into the oesophagus are inhibited. Since gas is produced very rapidly in the rumen, bloat can develop very suddenly.

Bloat reduction tips:

- The risk of bloat decreases substantially with advancing maturity of the legume. Alfalfa in the vegetative to early bud stages of growth is most likely to cause bloat.

- Grazing or feeding systems that are continuous are less likely to induce bloat than those that are interrupted.

- Cattle should be turned out to new pastures in the afternoon rather than in the morning when dew might still be on the alfalfa or clover.

- Swathing and wilting alfalfa prior to grazing reduces the risk of bloat. For example, bloat was reduced by 70% when alfalfa was swathed and wilted for 24 to 48 hours as compared to direct grazing.

- Pasture management that promotes continuous and rapid ruminal clearance (more bypass, less gas production--see Ch. 7) is likely to reduce the incidence of bloat.

Bloat misconceptions:

- The notion that alfalfa is bloat-safe after a killing frost is unfounded.

- Mineral supplements and household detergent ('Tide®') have proved ineffective for reducing bloat under experimental conditions.

New research

New research from Agriculture & Agri-Food Canada (Kamloops Research Centre) now provides the grazier with some additional tools for reducing the risk of bloat.

- A new variety of alfalfa with reduced tendency for causing bloat, called AC Grazeland, has recently been released by Agriculture & Agri-Food Canada. Tests in western Canada indicate that this cultivar may reduce the incidence of bloat by 60-85%. This variety features a lower initial rate of digestion in the rumen compared to conventional varieties. AC Grazeland is the product of more than 15 years of research.

- A number of legumes, such as sainfoin, birdsfoot trefoil and cicer milkvetch, do not cause bloat. The non-bloating characteristic of sainfoin is attributed to presence of a substance referred to as tannin. Tannins are absent in alfalfa. A recent study showed that feeding 10% sainfoin (dry matter basis) with alfalfa reduced the occurrence of bloat by 80-90% compared to pure alfalfa. Further research is needed on factors that control tannin content in sainfoin.

- A newly introduced legume called 'berseem clover' caused 85% less bloat than alfalfa.

- In an experiment at Kamloops, a product out of New Zealand, Blocare® 4511, was completely effective in the prevention of alfalfa bloat in Jersey steers. The product was added to the drinking water at a concentration of 0.1% and did not affect water consumption. (The most logical approach for administering anti-bloat agents is through the water supply.) Blocare® 4511 is not yet licensed in Canada.

Contributed by Walter Majak, Agriculture and Agri-Food Canada, Research Centre, Kamloops, BC.

Chapter 5: Nutrient Management

Whole Farm Perspective

Introduction

Livestock farms in coastal BC and the PNW are sinks for nutrients produced in other regions. Feed concentrates are railed in from the Prairies and the Midwest and alfalfa hay is trucked in from the interior of British Columbia, Alberta, Washington and Oregon. These imported feed stuffs bring mineral nutrients with them. Increasingly, dairy farms in the region have a surplus of nutrients coming onto the farm relative to products (milk, meat, forage) sold off the farm.

Nutrient management on livestock farms concerns control of (1) nutrient imports to the farm, (2) exports off the farm and (3) nutrient flows within the farm. Although forage systems are generally more sustainable and environmentally friendly than annual cropping, they can also be "leaky" when large quantities of nutrients and livestock wastes are handled. On dairy farms, typically only 20-33% of imported nutrients are exported as farm products while most of the remainder is lost to the environment.

Concern over leakage of surplus nutrients from livestock operations is world-wide. For example, in The Netherlands, allowable nutrient surpluses (inputs minus exports) are regulated on all livestock farms (Table 1). Note that there is a planned reduction in allowable surpluses until the year 2008.

Table 1.  The changing levels of allowable nutrient surpluses on livestock farms in The Netherlands
.

Year

.

1998

2000

2002

2005

2008

kg/ha (lb/ac)

Nitrogen

300 (270)

275 (250)

250 (220)

200 (180)

180 (160)

Phosphorus

17 (15)

15 (13)

13 (12)

11 (10)

9 (8)

1. Impact of Livestock Density on Nutrient Management

The challenge of managing nutrients increases when density of livestock per land area is increased. To facilitate comparisons, animal populations are described in terms of animal units. One animal unit (AU) is equal to a 450 kg (1000 lb) ruminant. Livestock density is defined as the number of AU's per unit of land area.

2. Impact of Housing and Storage Systems on Nutrient Management

The design and layout of a farm determines how manure nutrients are collected, stored and applied to the land.

On dairy farms, 25-70% of farm nitrogen is lost to the atmosphere during handling and storage of manure. Highest losses occur from lagoon/flush systems while lowest losses occur from slatted floor/covered pit storage. Covering manure storage and frequent barn cleaning help to conserve nitrogen. Barns with recycling flush systems are prone to elevated nitrogen losses even though they are typically cleaned 4-6 times per day. This is because the fluid is repeatedly aerated as the barn is flushed and because the storage facilities are usually very large and open.

Table 2 shows typical concentrations of nitrogen and dry matter in manure from typical housing and storage systems found on west-coast dairy farms.

Note that low nitrogen concentration in manure does not necessarily indicate that nitrogen has been lost. Rather, nitrogen concentration is correlated with dry matter content of the manure. Nitrogen concentration after storage is affected more by dilution of manure with rainwater and wash-water than by nitrogen loss during handling and storage (Table 2).

Table 2. Nitrogen concentration of dairy manure from different types ofhousing and storage (sources: Tunney and Sullifan, 1997 Oregon State University; Schmidt, 1997 Dairy Producers' Conservation Group).

System Description

Dry Matter

Total N
(kg/m3)*

Ammonium N
(kg/m3)*

Ammonium N
(% of Total N)

1. Slatted floor or barns scraped twice daily; roofed storage; minimal dilution

10%

3.0-4.5

1.5-2.2

50%

2. Barns scraped twice daily; uncovered above ground storage; minimal dilution

8%

2.2-4.0

1.1-2.0

50%

3. Barns scraped daily; uncovered concrete pit storage

6%

1.7-3.5

0.9-1.7

50%

4. Barns scraped daily; single cell lagoon storage

4%

1.2-3.0

0.6-1.5

50%

5. Flush barn; solid/liquid separation; 2 or 3 cell lagoon storage

0.5-1.2

0.4-1.0

60-80%

The type of housing and storage system also influences how the manure is applied to the land. On many low- and medium-density dairy farms, manure is mechanically scraped from the barns to the storage facility. Some of these barns have slatted floors with manure storage directly underneath. The manure on these farms averages 6-10% dry matter. These farms often use vacuum tanks (honey wagons) for land application, unless a custom slurry irrigation service is readily available.

The trend among high-intensity farms has been towards flush systems for barn cleaning and large earthen or concrete-lined lagoons for storage. Typically, these farms use solid/liquid separators to facilitate the flushing system. The liquid fraction of the stored manure often has less than 4% dry matter and sometimes even less than 2%. Because of the high volume of liquid handled, high-density farms tend to use irrigation systems to apply manure.

3. Impact of Feeding System on Nutrient Management

Within the limits of her genetic potential, a cow's production is a function of the quality and quantity of her feed intake. New feed-balancing computer models, such as the Cornell Net Carbohydrate Protein System, have greatly improved ration formulation (see Ch. 7).

The forage component of a ration (grass or grass-legume and corn) ideally contains 43% neutral detergent fibre (NDF), 33% non-structural carbohydrates (NSC - 100% as starch), 13.5% crude protein (CP) and less than 11% ash. All carbohydrate components should be highly rumen degradable. The crude protein would be 60% soluble, and this soluble protein may contain up to 65% non-protein nitrogen.

The balance of the diet comprises concentrate containing entirely degradable non-structural carbohydrates along with the appropriate proportion of rumen degradable and rumen by-pass protein. Rumeninert fat would also be supplemented.

Table 3 - How Management Affects

Nitrogen Efficiency On Dairy Farms

(Case Studes of Three Dairy Farms In The UK)

Farm 1 Farm 2 Farm 3
Inputs: kg nitrogen/ha (lb nitrogen / ac)
Fertilizer 319 (287) 190 (171) 142 (128)
Feed 120 (108) 115 (104) 89 (80)
Atmosphere 30 (27) 30 (27) 30 (27)
Total 469 (422) 335 (302) 261 (235)
Outputs
Milk 66 (59) 64 (58) 55 (50)
Animal 6 (5) 7 (6) 5 (5)
Total 72 (64) 71 (64) 60 (55)
Surplus 397 (358) 264 (238) 201 (180)
Leached N 61 (55) 30 (27) 28 (25)
Nitrogen Efficiency OF Whole Farm (%)
Farm product / All inputs 15 21 23
Farm product / Purchased inputs 16 23 26
Farm product / Surplus 18 27 30

Farm 1

Good commercial practice High output

- Economic optimum rate of nitrogen application

- Slurry stored for 1 month

- Supplementary feed: 18% protein at least cost.

Farm 2

Reduced loss High output

- Corn with relay crop

- Diet to minimize degradable protein

- Tactical nitrogen application

- No slurry: Sept. to Nov.

- Slurry on corn: rapidly ploughing in

- Slurry on grass: diluted before broadcasting.

Farm 3

Minimal loss Reduced intensity

- Corn with relay crop

- Diet to minimize degradable protein

- Reduction in fertilizer nitrogen application

- No slurry: Sept. to Jan.

- Slurry on corn: rapidly ploughed in

- Slurry on grass: by shallow-slit injection.

(adapted from S. Peel, A.G. Chalmers, and S.J. Lane

How does the diet affect the efficiency of nitrogen use? Milk nitrogen efficiency is defined as milk nitrogen output divided by off-farm inputs of feed, fertilizer and atmospheric nitrogen. Improving the diet to increase annual milk production from 8200 to 10,000 kg (18,000 to 22,000 lb) increases milk nitrogen efficiency only from 32 to 35%. Deviating from the ideal ration increases urinary or faecal nitrogen. For example, if the crude protein in the forage component is increased from 13.5 to 18.5% without adjusting the supplement, and all the additional protein is rumen degradable, excretion of nitrogen in the urine will double.

Does improved feeding efficiency mean that the farm is more sustainable? Yes, if the feed is mostly home-grown and closely matches the nutritional need of the cows. But if more feed must be brought in to feed the cows more efficiently, the net impact is greater nutrient loading of the available land base.

In intensive grazing systems that rely on home-grown grass herbage for a very high proportion of the diet, nitrogen efficiency of the cows may be comparatively low. Rapidly growing grasses are highly digestible and contain up to 20-25% crude protein. These diets are high in rumen degradable protein and low in energy. Hence, proportionately more nitrogen is lost as urine or faeces and nitrogen efficiency of the cow is low. However, because nitrogen imports to these farms are often low, the overall effect from a nitrogen budgeting perspective is generally favourable. (In good grazing systems, relatively more nitrogen is lost to the atmosphere than surface or ground water.)

The challenge for researchers today is to help producers grow as much of their feed requirements as possible and to match the nutritional quality of home-grown feeds to nutritional needs of cows. Reducing imported feeds means reducing excess nutrients!

Table 4 - How Management Affects

Nitrogen Efficiency On Dairy Farms

(Case Studes of Three Dairy Farms In Washington State)

Farm 1 Farm 2 Farm 3
Inputs: kg nitrogen/ha (lb nitrogen / ac)
Fertilizer 3 (3) 100 (90) 111 (100)
Feed 800 (720) 659 (593) 87 (78)
Atmosphere 30 (27) 30 (27) 30 (27)
Total 833 (750) 789 (710) 228 (205)
Outputs
Milk 228 (205) 240 (216) 64 (58)
Animal 2 (2) -10 (-9) 0 (0)
Total 230 (207) 282 (254) 64 (58)
Surplus 603 (543) 507 (456) 164 (148)
Nitrogen Efficiency OF Whole Farm (%)
Farm product / All inputs 28 36 40
Farm product / Purchased inputs 29 37 32
Farm product / Surplus 38 56 39
Farm Profile
Herd Size 418 994 40
Corn - hectares (acres) 36 (89) 77 (190) 0 (0)
Grass - hectares (acres) 46 (114) 154 (380) 22 (54)
(adapted from C.G. Cooger, T.N. Cramer, A.I. Bary, and D.C. Grusenmeyer. WSU, Puyallup, WA (unpublished data).

 

Nutrient Cycling in Forage Crops

 

Fig 1. Nitrogen cycle. Adapted from D.M. Ball, C.S. Hoveland and G.D. Lacefield. 1991. Southern Forages. Potash and Phosphate Institute and Foundation for Agronomic Research, Norcross, GA. 256pp.

 

Inputs

Plants obtain most of their nutrients from the pool of dissolved nutrients in the soil. This solution is constantly being replenished from three sources: inputs (manure, fertilizer, and other amendments), decomposing organic matter, and release of nutrients held weakly by the soil particles (mainly nutrients with a positive charge such as calcium, potassium, magnesium and ammonium). Small amounts of nutrients may be deposited in rainwater (ammonium, sulphate) or applied in irrigation water (nitrate).

Note that the negatively charged nutrients (nitrate, phosphate, and sulphate) are generally not held by soil particles so they do not take part in the exchange with the soil.

kg/ha (lb/ac)
Location Nitrogen Phosphorus Potassium
British Columbia 180-620

(160-550)

40-170

(35-150)

95-155

(85-140)

Washington 195-820

(180-740)

70-185

(60-170)

64-410

(60-370)

Table 5. Annual nutrient inputs on dairy farms in western BC and Washington.

The ranges for nutrient inputs to British Columbia and Washington dairy farms are listed in Table 5. Note the very wide range of inputs among farms. By comparison, annual nutrient inputs on UK dairy farms average 380 kg/ha (339 lb/ac) of nitrogen, 36 (32) of phosphorus and 266 (221) of potassium. Much lower inputs are supplied in the pastoral systems of New Zealand.

Plant Uptake

Forage crops harvested in south-coastal BC typically contain 2-4% N, 0.2-0.4% P, 2.0-4.0% K and 0.3-0.4% S. Average values for these nutrients in samples submitted to the South coastal Forage Competition from the 1993-97 crop years are shown in Table 6.

Assuming annual yields of 13 t/ha (6.0 ton/ac), the amount of nutrient removed from the soil in a single year is: 360 kg/ha (325 lb/ac) of nitrogen, 45 (40) of phosphorus, 400 (360) of potassium, 30 (27) of magnesium and 35 (32) of sulphur. The pattern of nutrient uptake and growth depends on weather patterns and harvest management. Note that 40% of the total plant nitrogen and a similar proportion of other nutrients remain in the unharvested portion of the plant (stem bases below cutting height, crowns and roots).

Carbon to Nitrogen (C:N) Ratio

In soils, mineralization and immobilization of nitrogen happen simultaneously. The balance between these processes is influenced by the C:N ratio of the organic materials in the soil. Organic material with a high C:N ration (e.g. straw, sawdust, etc.) promotes microbial growth which consumes mineral nitrogen in the soil. These types of materials create a shortage of nitrogen for the crop. If the amount of mineral N exceeds that which is necessary for microbial growth, surplus N will be released.

  • Immobilization exceeds mineralization if organic addition has a C:N ratio greater than 30:1.
  • Immobilization equals mineralization when C:N ratios are between 15:1 and 30:1.
  • Mineralization exceeds immobilization when C:N ratios are less than 15:1.

C:N ratios of common organic materials

Material C:N Material C:N
Laying hen manure 6:1 Dairy pen straw 24:1*
Soil humus 10-15:1 Horse manure 30:1
Swine manure 14:1 Separated dairy manure solids 62:1*
Broiler litter 14:1 Corn stalks 67:1
Sheep manure 16:1 Straw 80:1
Dairy manure (liquid) 16:1* Paper pulp 100:1
Grass clippings 17:1 Sawdust 400:1
Newsprint 625:1
*Based on T.N. Cramer (unpublished data)

Up to 50% of the herbage may become senescent before harvesting. The dying leaves at the base of grass plants release some of their nutrients which are stored in the crowns. The dead leaves are left with a high carbon to nitrogen (C:N) ratio so that they are slow to decompose and form a part of the thatch, characteristic of old grass stands.

Animal Intake and Excretion

Ruminants retain only about 25% of consumed nitrogen, 35% of phosphorus and 12% of potassium. The remainder of the consumed nutrients is excreted. With ideal protein content (see Ch. 7), cows excrete more than twice as much nitrogen in faeces as in urine. However, with increasing protein or increasing rumen degradability of protein, the amount and percentage of nitrogen excreted as urine rises. Under local conditions, about equal amounts of nitrogen are excreted in faeces as in urine.

In contrast, phosphorus is excreted primarily in faeces whereas potassium is excreted mostly in urine. Large variations in composition of stored manure, inability to regulate the individual nutrients, and problems in methods of application complicate the use of manure as the primary nutrient source in grass production.

Mineralization of Nutrients

Table 6. Average nutrient composition of grass hay and silage entries in 'South Coastal British Columbia Forage Competition' (1993-1997)
Nutrient Grass

Hay %

Grass

Silage %

Nutrient

Removal

By Crop

Nitrogen 2.8 2.8 360 (325)
Phosphorus 0.33 0.37 45 (40)
Potassium 3.1 3.1 400 (360)
Magnesium 0.23 0.24 30 (27)
Calcium 0.47 0.56 65 (60)
In kg/ha or (lb/ac) based on a crop yield of 13 t/ha (6.0 T/ac) dry matter basis.

Mineralization refers to the process of microbial decomposition of organic material that releases mineral nutrients into the soil. Plants take up nutrients only in the mineral form. For example, microbes break down proteins and other forms of organic nitrogen into the mineral form, ammonium. Other microbes further convert ammonium into nitrate (see Fig. 1

The mineralization rate is dependent largely on the carbon to nitrogen (C:N) ratio in the soil organic matter. In agricultural soils, the C:N ratio in the organic matter ranges from 10:1 to 15:1. The majority of the soil organic matter is very stable so the organic matter content of the soil does not change much from year to year. Similarly, organic amendments that contain at least 25 times more carbon than nitrogen do not easily break down. The stable organic matter becomes the humus fraction of the soil and improves the physical properties and cation exchange of the soil. Organic matter is more stable and tends to accumulate more in clay than in sandy soil. The reason is that clay soil is less aerated and has more surface area to adsorb organic colloids.

Only the much smaller 'degradable' pool easily mineralizes and provides fresh nutrients. Rate of mineralization is strongly enhanced by a history of manure and fertilizer application. Mineralization is more active in well drained than poorly drained soils, especially when they are warm. For unknown reasons, freshly generated populations of microorganisms (e.g. after drought or freezing events) mineralize organic matter more aggressively than stable older populations. Many species of protozoa, fungi, nematodes, and earthworms are active in mineralization (see "Notes from the Underground").

Soils on most dairy farms in the coastal region have long histories of manure application. Recent research out of Washington State indicates that mineralization rates on fields with a history of manure application can be nearly double those of non-manured fields. Over the growing season, the impact of this may be a release of up to 220 kg N/ha (200 lb/ac). This must be accounted for in nutrient management plans. Values up to 400 kg/ha (360 lb/ac) of mineralized nitrogen have been reported from a single year in the UK. (In the UK 20-40% of all mineralization occurred in November to February.)

It is clearly important to predict mineralization rates to determine fertilizer requirements. Unfortunately no such commercial test is yet available anywhere in the world. The best approach for producers is to assess their fields with test strips.

Did You Know

Rain containing ammonia (referred to as acid rain) is actually alkaline, not acidic. But when this rain falls on the soil, the ammonia is oxidized causing the soil to acidify. Thus 'acid rain' should be renamed 'acidifying rain'. (Courtesy of D. Sullivan, OSU)

* Note: mineralization of sulphur follows that of nitrogen, but phosphorus processes are more complex.

Evidence that applied nitrogen is immobilized (tied up) and re-released in BC forage soils

Did You Know
Rain containing ammonia (referred to as acid rain) is actually alkaline, not acidic. But when this rain falls on the soil, the ammonia is oxidized causing the soil to acidify. Thus 'acid rain' should be renamed 'acidifying rain'. (Courtesy of D. Sullivan, OSU)

Both forms of inorganic nitrogen (nitrate and ammonium) can be either absorbed by grass or assimilated into new microbes. Mineral nitrogen captured by microbes is said to be immobilized. When nitrogen is applied to grass there is fierce competition between crop and microbes and the crop does not totally win.

This phenomenon was observed by researchers at PARC (Agassiz). In their study, 400 kg/ha (360 lb/ac) of nitrogen was applied as a single dose in March. The crop was harvested four times over the season, with the fourth harvest in October. Judging by yields in the final harvest, it appeared that much of the benefit of the March dose had disappeared.

But this was not the case! In two of three years that this trial was done, the March application of nitrogen left a profound effect on plant nitrate and crude protein content in the fourth harvest, about six months after the fertilizer was applied (Table 7). This delayed effect was surely due to the nitrogen being immobilized through the season by soil microorganisms. Such responses demonstrate that nitrogen transformations within agricultural soils are very dynamic.

 

 Fig. 2. Manure run-off into surface waterways is harmful to fish habitat.

Loss of Nutrients from Forage Fields

Environmental Consequences of Nutrient Losses

1. Nitrogen leached as nitrate may contaminate ground water.

2. Nitrogen runoff as ammonium or organic matter is detrimental to surface waters and very harmful to fish habitat.

3. Nitrogen is lost to the atmosphere as nitrogen gas (not harmful), as nitrous oxide (potent greenhouse gas), and as ammonia (forming acid rain and fine particulates that are harmful to lungs).

4. Phosphorus (and organic matter) which runs off into surface waters promotes the growth of algae which eventually deplete dissolved oxygen and cause the water to become murky so that fish are unable to thrive. Phosphorus may leach from soils containing very high levels. Leached phosphorus may eventually seep into surface waters.

5. Leached potassium and sulphur are thought to have little environmental impact at present.

Ammonia Loss by Volatilization

Ammonia volatilizes (evaporates) from livestock housing and waste storage facilities. Ammonia is also lost from application of manure, application of ammonia and urea fertilizers, and even directly from plants. From 30 - 80% of ammonium nitrogen in slurry may be lost during field application, with the greatest losses immediately after application. Efficient methods of manure application are discussed below.

Table 7: Nitrate-nitrogen and crude protein in fourth harvest of orchardgrass (October) as affected by nitrogen applied in March for the first harvest of the same year.
Nitrogen Rate
(kg N/ha)
N itrate-N (ppm) Crude Protein (%)
1989 1990 1991 1989 1990 1991
0 82 95 25 19.9 14.9 14.3
400 69 1748 1116 16.3 16.7 16.9

Nitrate Loss by Denitrification

Whereas ammonia is volatile and readily evaporates, nitrate can be lost only through leaching (see below) and denitrification. Denitrification is a biological process carried out by anaerobic bacteria that substitute nitrate for oxygen in their metabolism when oxygen is not available. The nitrate is degraded into atmospheric nitrogen or nitrous oxide. Whereas atmospheric nitrogen is obviously not harmful, nitrous oxide is a potent 'greenhouse gas,' helping to trap heat in the atmosphere.

Annual losses by denitrification can be substantial, ranging from 15 - 110 kg nitrogen/ha (13-100 lb/ac). Daily nitrogen losses can be as high as 2 kg/ha (2 lb/ac). The process is most rapid in warm, saturated, anaerobic soils containing a lot of nitrate.

Nutrient Losses by Leaching and Runoff

Greatest risk of leaching occurs during the high rainfall period lasting from October to March. The risk of leaching from forage fields is much smaller than from annual crops because of the well-developed root system and microbial population. In fact, forage systems were once considered impervious to leaching. However, new information from many countries has shown that substantial leaching may occur from heavily fertilized forage crops. History of manure and fertilizer management, age of sward, soil conditions, drainage and weather patterns affect the amount of leaching.

i. NITROGEN

There have been relatively few direct measurements of leaching from forage fields in south-coastal BC or the Pacific Northwest. Productive grass stands that receive less than 400 kg/ha (360 lb/ac) of nitrogen usually have little soil nitrate left in fall. However, environmental conditions favouring high rates of mineralization may result in unexpectedly high soil nitrate levels. Research in England has shown higher rates of nitrogen leaching from grasslands in the fall after a hot dry summer than after a cool wet one. Amounts of residual soil nitrate after fall application of manure in BC are shown below (See 'Fall Manure Application,' Pg. 42).

A new concern is the leaching of organic nitrogen. This form of nitrogen may eventually find its way to surface waters, contributing to eutrophication. More organic nitrogen is leached from grass-legume stands than from pure grass stands.

ii. PHOSPHORUS

In the past, leaching of phosphorus was thought to be negligible because of the immobility of phosphate in the soil. Now, seeping of leached phosphorus is considered a possible threat for surface waters.

Leaching of inorganic phosphorus is known to occur when the sorption capacity of the soil is saturated. Also, phosphorus in the organic form can leach from fields with a history of heavy manure or phosphorus fertilizer application. A recent study in Australia demonstrated that a third of applied phosphorus might leach through soils that have large numbers of macropores (cracks). In the Australia study, a single rainfall event leached as much as 0.5 kg/ha (0.4 lb/ac) of phosphorus.

Nevertheless, runoff of phosphorus remains the greater concern, with losses reaching 2 kg P/ha (1.8 lb/ac) in snow-melt and over 0.5 kg P/ha (0.4 lb P/ac) from spring rains.

iii. POTASSIUM

Recent information from farm potassium budgets in Coastal BC and the PNW imply that leaching of potassium can occur on some farms. Leaching losses would be higher from sandy than from fine-textured soils. Runoff losses of potassium as high as 30 kg/ha (27 lb/ac) have been recorded after application of farmyard manure in October. Loss of potassium is not considered to be an environmental concern at present.

iv. SULFUR

Leaching of sulphate coincides with leaching of nitrate as both ions are negatively charged and mobile in the soil. Losses ranging from 11 - 29 kg S/ha (10-25 lb S/ac) have been measured in the UK and New Zealand. Leaching of sulphate is not a significant environmental concern at present.

The Latest Information On Nitrogen Fertilization

How much nitrogen for optimum production?

Figure 3 shows the wide range possible for response of grass to fertilizer nitrogen. In all trials, 400 kg/ha (360 lb/ac) of nitrogen produced near maximum yields of approximately 16t/ha (7.1 ton/ac), but the trials differed widely in the yield benefit from fertilizer.

In 1991, fertilizer increased yield by 8 t/ha (3.6 ton/ac) of dry matter whereas in 1989 the increase was only 2 t/ha (0.9 ton/ac). In the 1989 trial most of the nitrogen required by the crop was released (mineralized) from the soil, whereas nitrogen released from the soil in the 1991 trial could support only half the potential grass yield. Mineralization of soil nitrogen is discussed above (see Nutrient Cycling).

Is there a test to predict how much nitrogen the soil will release over the growing season? For corn crops, the 'pre-sidedress nitrogen test' is used to indicate whether nitrogen fertilizer is likely to be required on a particular field. Unfortunately, grass systems are more dynamic and no such test has yet been found. At present, use of test strips with different application rates is the best approach. Pasture probes can be used to help estimate yield differences among the strips.

 

Fig 3. Range of yield responses by unirrigated forage grasses to application of nitrogen fertilizer in coastal BC (for lb/ac multiply kg/ha by 0.9 and for T/ac multiply t/ha by 0.45)

Fig 4. Seasonal effect of nitrogen fertilizer on grass (tall fescue) yields in coastal BC. Trials were conducted without irrigation in 1994-96 (for lb/ac multiply kg/ha by 0.9 and for T/ac multiply t/ha by 0.45).

When to Apply Nitrogen Fertilizer

Which harvest responds most to nitrogen?

Between a quarter and a third of annual production is harvested in the first cut. Lengthening days, ample moisture, stem elongation and use of root reserves contribute to the high spring production. The yields of our cool-season forages are lower in summer than in spring because of high temperatures, shortening days and water deficits. Fall production benefits from better temperatures and moisture but suffers from the short daylength.

A study at PARC (Agassiz) showed that grass both produces most herbage and needs most nitrogen in spring (Fig. 4; shows the yield for three of the five harvests taken). Both yield and nitrogen requirements were lower in summer and declined further in fall. In these trials, optimum nitrogen rates would be 75-125 kg/ha (70-110 lb/ac) in May, 50-100 kg/ha (45-90 lb/ac) in July and 25-75 kg/ha (25-70 lb/ac) in September.

What happens if you apply all the nitrogen in spring?

To answer this question, researchers at PARC (Agassiz) compared 400 kg nitrogen/ha (360 lb/ac) as a one-time spring application or as four equal applications of 100 kg/ha (90 lb/ac) over the growing season.

The results were surprising and instructive. The great differences in pattern of fertilizer application had only a small effect on total yield (Table 8) or average crude protein content of the crop. These results show the dynamic yet stable nature of forage production.

In contrast, fertilizer distributions do produce important differences in nitrate concentration in plant tissue. In the first crop taken after applying 400 kg N/ha (360 lb/ac), concentrations of nitrate-nitrogen averaged 3800 parts per million (ppm), more than three times the recommended maximum level. Concentrations of nitrate-nitrogen declined progressively in later harvests, falling to 1000 ppm by the fourth harvest. When nitrogen was applied in four equal doses of 100 kg/ha (90 lb/ac), nitrate-N concentration ranged from 1400-2200 ppm (see Figs. 23 and 24). (Note that nitrate content is reported either as nitrate or nitrate-N concentration. To convert nitrate to nitrate-N divide by 4.)

Table 8: Effect of distribution pattern for nitrogen fertilizer on total annual herbage yield.

Fertilizer Applications * Dry Matter Yield

T/ha (ton/ac)

Relative to Equally Distributed N
100-100-100-100 14.8 (6.7) 100%
400-0-0-0 14.1 (6.3) 95%

Grass response to delayed fertilizer application.

Farmers are often faced with delayed application of fertilizer after harvest. What the crude protein content of the grass. Therefore, the overall effect of delayed application on uptake of nitrogen was very small. Delaying fertilizer application increases the content of nitrate in the herbage.

'T-Sum' Method for Timing Spring Nitrogen

'T-Sum' is a method to determine when to make the first application of nitrogen fertilizer in spring. The 'T-Sum' value is the accumulated mean daily temperatures (in ° C) above zero, starting on January 1 (below-zero temperatures are ignored). For example, if the mean daily temperatures for a 5-day period were 6, 3, 0, 1, and -4°C, the 'T-Sum' total is 10. The 'T-Sum' concept assumes that rate of spring growth is related to accumulated mean temperature.

In the UK, the 'T-Sum' value of 200 is widely accepted for applying spring nitrogen and 'T-Sum' information is published weekly. In a study at PARC (Agassiz), fertilizing at 'T-Sum' 300 produced first-cut yields that were marginally higher than at 'T-Sum' 200, while uptake of nitrogen was about 10% higher (Table 9). The late-maturing variety did not benefit more from higher 'T-Sum' values. 'T-Sum' was not affected by source of nitrogen (ammonium nitrate vs. urea). An earlier study at Agassiz and on Vancouver Island showed a slight advantage for 'T-Sum' 200.

Table 9. The effect of applying nitrogen by 'T-Sum' value on yield and nitrogen uptake of early and late maturing grasses at PARC (Agassiz)*

T-Sum
200 300 200 300
Yield

- t/ha (T/ac) -
Nitrogen Uptake

- kg/ha (lb/ac) -
Early Maturing
Orchardgrass 'Benchmark' 3.5

(1.6)

3.5

(1.6)

3.5

(1.6)

3.5

(1.6)

Tall fescue 'Maximize' 3.2

(1.4)

3.3

(1.5)

51

(46)

46

(40)

Late Maturing
Orchardgrass 'Mobite' 3.7

(1.7)

4.0

(1.8)

51

(46)

56

(50)

*This study was supported by Westco Fertilizers Ltd., Calgary, AB

Tips on First Cut Nitrogen Management

Consider that 25 to 40% of the annual grass yield is taken in the first cut. Clearly, spring forage management is critical to feed production on the farm.

-When harvested at the same growth stage, late-maturing varieties of orchardgrass (e.g. Mobite), perennial ryegrass (e.g. Melle) and tall fescue (e.g. Courtenay) have higher yield but lower protein content than early-maturing varieties. Therefore, late-maturing varieties should be given more nitrogen than early varieties to support the high level of growth and maintain protein levels. It is wise to harvest late varieties at a slightly earlier growth stage than early-maturing grasses (See Ch. 7).

-Urea and ammonium nitrate sources are generally of similar effectiveness (urea may actually be slightly better for late-maturing grasses.)

-In coastal BC, 'T-Sum' 300 is slightly better than 'T-Sum' 200 for applying nitrogen fertilizer (see 'T-Sum').

-Factors such as slope and aspect (i.e. south vs. north) and drainage (well-drained soils warm up faster in spring) can influence optimum timing for fertilization.

Management Of Nutrients In Manure

 

Fig. 6. Fixed passive manure separation with two cells.

In intensive livestock enterprises, manure can often supply most of the nutrient requirements of forage crops grown on the farm. The key is identifying a management system that will make the most efficient use of the manure nutrients.

Historically, most of the manure on local dairy farms was applied to corn land before planting in spring and after harvest in fall. After-harvest application in fall is strongly discouraged. Applying rates exceeding corn demands in spring will cause unacceptable residual nitrogen levels in the soil after harvest. Logically, manure should be applied primarily on grassland. Grass crops have a high nutrient requirement, can receive manure throughout the season and have a well-developed root-soil system for capturing nutrients and preventing leaching.

 

 Fig 7. Effect of slurry dry matter content on volatilization of ammonia (as percent of applied ammonia)

Unfortunately, it is difficult for farmers to use slurry as the primary nutrient source for grass production for the following reasons: nutrient concentration is unknown, uniform application with current equipment is difficult, risk of smothering and fouling of leaves is possible, and the efficacy is variable. In fact, up to 80% of the ammonium in manure may be lost during field application with vacuum tanks or irrigation reels. Amount of loss depends on weather conditions, ammonium concentration, dry matter content and application rates (Fig. 7)

 

 

Strategies to overcome the "thick manure" problem:

When upgrading manure storage, many farmers have built 2-cell storage. The first cell is used primarily for settling and the second for liquid storage. If the material entering the first cell is in the 8-10% dry matter range, the liquid entering the second cell will typically be around 4-6%. The manure in the second cell contains proportionately more of the ammonium-nitrogen and potassium but less of the organic nitrogen and phosphorus.

Some farms have installed mechanical separators to remove the solids. Numerous options are available with a wide range of prices and solid removal efficiencies. The dry matter content of the liquid fraction is usually less than 4%, even if the starting material is quite thick. At least 60% of the nitrogen in the liquid fraction is in the ammonia form. Grass response to separated liquid is excellent (see Fig. 8).

Some farms dilute slurry with water for irrigating on forage crops. Hauling diluted slurry seems impractical.

Following manure application with irrigation helps reduce ammonia loss.

'Whey' is reputed to stimulate microbial activity and may reduce the amount of solids. In a local study, whey reduced the solids content of liquid manure in 2 of 3 experiments (Schmidt and Paul, 1997).

Studies in Northern Ireland have shown that adding strong acids (nitric or sulphuric) to slurry greatly reduces ammonia loss but this practice is not economical.

Dairy Or Hog Manure - Which Is Better?

A study at PARC (Agassiz) compared the effectiveness of dairy and hog manure as a nitrogen source for grass (tall fescue). Hog manure typically contains a higher proportion of its nitrogen as inorganic ammonium compared to dairy manure. In this study, both manure types were equally effective when applied at the same rate of inorganic nitrogen. The ammonium in hog manure, applied with the conventional splash-plate, was 5-10% less effective than inorganic fertilizer in terms of grass yield and crude protein content. Therefore, to achieve the same grass performance, slightly higher application rates should be used. Banding hog manure improves its efficacy and reduces odour (see below). Hog manure can be safely used as the primary nitrogen source for grasses like tall fescue provided that it is applied at agronomic rates. Phosphorus levels in the soil should be monitored.

 

 

 Fig. 9. Separating manure produces a solid fraction high in organic-N and phosphorus and a liquid portion high in ammonium-N and potassium.

1. Influence of Form and Dry Matter Content of Manure

To maximize use of nitrogen from manure, the primary goal is to reduce ammonia loss. To a degree, this can be accomplished by altering the form and dry matter content of the manure. Manure in the 8-10% dry matter range is like thick soup and has these undesirable properties:

i. Thick manure does not soak well into the soil unless rain or irrigation follows application.

ii. Thick slurry clings to grass leaves increasing exposed surface area and contributing to ammonia loss. Reducing dry matter of slurry reduces ammonia losses appreciably (Fig. 7)

iii. The adherence of manure to leaves can also 'burn' the grass, reducing the quality and palatability of the forage.

 

 Fig 8. Response of grass crops to forms of dairy manure at PARC, Agassiz (for lb/ac multiply kg/ha by 0.9 and for T/ac multiply t/ha by 0.45).

2. Influence of Method of Manure Application

A. Banding Systems for Slurry

Injection systems are used to reduce ammonia loss from slurry applied to cultivated land (Fig. 10). However, this technique cannot be easily used on grassland because of equipment costs, reduced rate of application, stones, and damage to stands. Nevertheless, interest in injection has been recently revived in some regions due to concern over nutrient runoff into streams.

To overcome the difficulties of injection into grassland, a system was developed for applying manure in bands on the soil surface underneath the grass canopy. This 'sub-canopy band application system' (see Fig. 11) chops the slurry then delivers it via individual hoses to shoes which drag along the ground surface beneath the grass canopy. Locally, the applicator has been given the name 'sleighfoot' to reflect its appearance and motion. European studies have shown that slurry applied with sleighfoot applicators loses much less ammonium and gives off less odor than slurry applied with conventional spreaders.

A recent study at PARC (Agassiz) compared the response of grass to dairy slurry. The slurry was applied with either a splash plate or sleighfoot applicator and granular fertilizer. The tests were conducted in spring, summer and autumn. The rate of application was set to supply 50 and 100 kg/ha (45 and 90 lb/ac) of ammonium-nitrogen per cut.

A Farmers Observation
Benefits of the Sleightfoot For Applying Biosolids on Grass

At Woodwynn Farm, located on southern Vancouver Island, we use biosolids from the Capital Regional District to supply the nutrients for our market hay operation. Our interest in the sleighfoot came from the odour management standpoint. For two years we evaluated the prototype unit which was used in the trials at PARC (Agassiz). We found that the way in which the material was deposited at the base of the grass reduced odour substantially. The grass acted as a barrier to smell. We suspect that direct soil contact is helping to reduce loss of ammonia from the biosolids to the atmosphere.

In 1997, Woodwynn Farm purchased an 8000-liter (2000 US gal) tank with a 6-meter wide (20-foot) sleighfoot unit made in Holland by Buts Meulepas. We chose to surface-band rather than inject manure because the banding unit requires half the power of injection units to pull around the field. Also, banding does no root pruning unlike injectors. We also believe that placing manure on the soil surface where it is exposed to sun and air reduces pathogens.

As this machine was extensively used we discovered other advantages of this application technology for our farm:

  • Precision placement: Buffer zones of 30 meters (100 ft) are required on fields that border ditches, streams and roads. The sleighfoot is so accurate in its placement compared to regular manure spreaders that a reduction in buffer widths was sometimes approved by BC Ministry of Environment, Lands and Parks.
  • Precise metering: We can control application rates with ease. This makes it easier to adhere to permits.
  • Uniform application: The distributor head makes for the same rate of application across the entire 6-m boom so there are no feathered edges.
  • No contamination: This was a big concern with the broadcast applicator, as our customers were concerned that their stock (mostly horses) would be ingesting biosolids. The sleighfoot does a great job of placing the material at the base of the grass which is not picked up in the harvested hay.
  • Invisibility factor: Our farm is ringed by houses and roads. The sleighfoot operates in such a way that the biosolids are never seen by our neighbours (as opposed to splash plate or irrigation systems). This is another perception benefit that seems to be important.

Contributed by Curtis Strong, P.Ag., Woodwynn Farm

Table 10: Horizontal uniformity of spreading pattern for tank-based manure application systems.
Manure Application System Form of Manure Variation (%)
Stationary splash plate Liquid pig - 4.8% dry matter 21
Swiveling splash plate Separated liquid pig - 3.8% dry matter 18
Lateral boom with equally spaced nozzles Liquid pig - 3.6% dry matter 31
Trailing hoses linked to central distributor Separated liquid pig - 3.8% dry matter 14

In all three seasons, grass receiving banded manure yielded about as much as grass receiving purchased fertilizer -when compared at equivalent rates of mineral nitrogen. In contrast, response of grass to slurry applied with the splash plate was inconsistent, ranging from equivalent to much less (1.3 t/ha or 0.5 ton/ac) than fertilizer.

 

 Fig.10. Shallow injection of manure into sod.

This study has a number of key implications for manure use in the future:

1. Banding of manure with the sleighfoot applicator is a consistent technique for supplying nitrogen to forage throughout the growing season. Appropriately applied manure can provide all the nutritional requirements of a productive grass stand.

Fig.11. Banding of manure with the sleigh foot applicator is an effective method of applying slurry on grassland.

2. The sleighfoot spreads slurry evenly.

3. Banding with the sleighfoot widens the window of opportunity for application. Manure will not burn or contaminate grass even 10-14 days after harvest. In fact, ammonia loss is even lower when the grass is tall.

4. The sleighfoot reduces odour during land application of slurry (including swine).

  Fig.12. Sleighfoot applicator leaves little manure on crop (left) compared to splash plate (right).

5. The fertilizer value of manure can be determined reliably using an inexpensive quick test (see section on manure analysis).

6. The overall benefits of the sleighfoot are reduced fertilizer expenses and less manure in the pit before winter.

B. Irrigation Systems for Slurry

With increasing farm size and increasing manure storage in recent years, there has been a growing interest in 'trailing gun irrigation systems' for application of manure. The primary advantage is that a large volume of manure can be applied in a relatively short period of time. Where custom services or rental services are available, many producers forego purchasing the systems in favour of hiring or renting.

 

Fig.13. Trailing gun irrigation system applies large volume of manure quickly but neighbours may be offended.

Slurry irrigation is often criticized because of the high odour levels emitted. This situation is made worse when concentrated slurries (6-10% dry matter) are applied. However, with careful management, irrigation can be an effective method of applying very dilute or separated liquid manure. As long as the solids content is low (

Influence of Timing of Manure Application

The common practice on grassland is to apply manure as soon as possible after harvest in order to supply the regrowth with nutrients quickly and reduce damage to the new regrowth. Unfortunately, it is difficult for farmers to apply manure as quickly as purchased fertilizer. Also, when there is little plant cover ammonia losses due to volatilization can be substantial. The sleighfoot applicator makes it possible to delay manure application with minimum contamination of grass leaves.

WHAT HAPPENS TO PRODUCTION WHEN MANURE APPLICATION AFTER HARVEST IS DELAYED?

Delaying fertilizer application by about a week reduced yield slightly but did not affect nitrogen uptake so nitrogen content in the herbage increased slightly (see above: 'When to Apply Nitrogen Fertilizer,' Pg. 33). In contrast, there was little evidence that a week delay in banding of slurry lowered either yield or nitrogen uptake. Manure that is banded into a growing grass canopy is sheltered from wind, thereby less prone to volatilization of ammonia, and may promote direct absorption of ammonia by the growing leaves.

Note that this study showed that manure increases grass growth most in spring and least in the fall (see 'Latest on Nitrogen Fertilization of Forages,' Pg. 32).

Importance of Uniformity of Application

Uniform manure application is necessary for optimum production and conservation of nutrients. Table 10 shows the relative variability for various tank-based spreading systems. Of course, systems that spray manure into the air are affected by wind.

Among the spreading systems tested, the conventional splash plate had intermediate uniformity (21%). An applicator employing a swivelling splash plate was slightly better. The lateral boom with nozzles was especially variable. The most uniform of the systems tested pumps manure from a central distributor to individual trailing hoses. The sleighfoot applicator uses the same distribution principle and has similar uniformity.

Table 11: Effect of repeated manure application on the composition and yield of a tall fescue stand.
Treatment Ground Cover (%)* Annual Yield
Grass Soil Clover t/ha (Ton/ac)
Control 56 8 35 10.8 (4.8)
Fertilizer - low rate 74 21 2 13.0 (5.8)
Fertilizer - high rate 70 27 1 14.5 (6.5)
Manure - low rate 75 26 0 13.9 (6.2)
Manure - high rate 57 43 1 16.6 (7.4)
*Totals may not add to 100 because moss and weeds are not included.

In contrast, variability of irrigation-based systems is usually higher, averaging 26-34% in one study and 15-22% in another. Irrigation systems are especially affected by wind conditions. Also, irrigation systems miss areas along field margins and headlands due to required setbacks and the circular distribution pattern. For these areas, farmers must use an alternative spreading method or inorganic fertilizer.

A new application method designed to improve on the uniformity of the "big gun" is called the trailing boom (Fig. 14). This system has downward directed nozzles and small splash plates equally spaced along the length of the boom. If the boom height and the pressure are set correctly, the system applies more uniformly and is less prone to drift than big irrigation guns.

Impact of Repeated Manure Applications on Grass- Positive or Negative?

We have seen that liquid manure can be used instead of fertilizer to fulfil the nitrogen requirements of grass, with little loss of yield or protein content. But what happens to the grass stand, the nutrient content of the soil and even the ecology of the soil (see "Notes from the underground," Pg. 40) after repeated applications of dairy slurry?

A study was set up at PARC (Agassiz) to compare applications of equivalent rates of inorganic nitrogen as chemical fertilizer or manure. In this trial, manure was applied with a sleighfoot manure applicator, which conserves nitrogen. With manure in the 6-8% dry matter range, the application rate was equivalent to 56 - 68 m3/ha (6000 to 7500 U.S. gal/ac). The organic nitrogen fraction in the manure was extra.

Fig 18. Effect of 3 years of manure or fertilizer nitrogen application to tall fescue stands on soil potassium levels (for lb/ac, multiply by 0.9).

YIELD AND STAND COMPOSITION:

In the third year of manure application, total yield was 9% higher and nitrogen uptake 5-9% higher from manured compared to fertilized treatments (see Table 11). In the fourth year, manured treatments yielded 10-21% more than fertilizer treatments. Higher yield and nitrogen uptake with manure than fertilizer is due partly to the use of an efficient application technique and partly to the release of additional nitrogen from the organic fraction of the manure. It also shows that there is no evidence that repeated manure applications reduce productivity of forage fields.

At the high rate of manure application (100 kg/ha or 90 lb/ac of mineral nitrogen), the grass stand became considerably sparser than at lower rates of manure or equivalent rates of fertilizer (see Table 11). The manured stand was left with more open space between plants. However, the surviving plants were bigger so that the overall yield of the manured grass was greater than the denser fertilized stands. If the amount of open space were to increase further, it is likely that eventually weeds (especially fine-leaf grasses like Kentucky bluegrass) would invade the open spaces and yield would fall off (see Ch 4 and Ch 6).

At low rates of application (50 kg/ha or 45 lb/ac of mineral nitrogen), there was little difference in stand composition between fertilizer and manure. Note that white clover aggressively invaded stands that did not receive fertilizer or manure.

Thinning of stands on manured fields is often blamed in part on tire damage and soil compaction. In this study, neither was a factor; manure directly caused thinning of stands.

EFFECT ON SOIL POTASSIUM AND PHOSPHORUS:

Liquid dairy manure contains substantial quantities of potassium (K), especially if the cattle diet is rich in potassium. Three years of repeated manure applications increased soil potassium levels by about 35%. Manured plots had 3.5 times more soil potassium than fertilized plots (Fig. 18). Note that nitrogen fertilizer actually reduced soil potassium levels from the starting levels. This shows that mineral fertilizer can be used to lower soil potassium levels.

Available soil phosphorus was marginally higher in manured than fertilized treatments in the top 15 cm (6 in) of soil. No difference in phosphorus level was found between treatments in the 15 - 30 cm (6 - 12 in) soil horizon, indicating that phosphorus had not moved downward in the three years.

 

 Fig 19. 'Apparent' recovery of nitrogen from fall-applied manure in the roots and shoots of tall fescue and fall rye at PARC (Agassiz). (#For lb/ac multiply by 0.9).

Impact of Applying Manure on Grass in the Fall

Throughout the region, on both sides of the border, regulations require that manure be applied on the land as a fertilizer source and not merely for the purpose of disposal. Thus, in the fall, manure must be spread on actively growing forages or on cover crops, not on bare corn fields. What happens to the nitrogen in manure spread on grass and cover crops in the fall?

Researchers at PARC (Agassiz) recently studied this question. They applied manure in mid-September or mid-October on grass and cover crops at rates of 100 or 200 kg/ha of total nitrogen (90 or 180 lb/ac). The cover crops fall rye and Italian ryegrass, were planted in mid-September.

By late November, the perennial rye-grass, tall fescue captured a total of 40 kg/ha (35 lb/ac) of the applied nitrogen, divided evenly in roots and shoots (Fig. 19). The fall rye cover crop captured only 10-15 kg/ha (9-14 lb/ac) of the manure nitrogen, most of it in the shoots.

Tall fescue reduced residual soil nitrate levels in late November by 20-30 kg N/ha (18-27 lb/ac) while fall rye reduced levels by about 10 kg/ha (9 lb/ac) (Fig. 20). Slightly less nitrogen was captured from manure applied in September than October but less nitrate was left in the soil from the September application.

Fig 20. Effect of crop type on ammount of nitrate-nitrogen remaining in the soil (120 cm or 48 in depth) in late November. Manure was applied in mid-September or mid-October at a rate of 200 kg/ha (180 lb/ac) total nitrogen. (*For lb/ac multiply by 0.9)

Both crops were dormant and captured little nitrogen between November and March (Fig. 19), but from late March to early May tall fescue recovered 25-35 kg/ha (22-31 lb/ac) of the manure nitrogen compared to 5-10 kg/ha (4-9 lb/ac) for fall rye. Tall fescue continued to take up nitrogen in May and June, particularly from the October-applied manure.

A total of 50-65kg/ha (45-60 lb/ac) of nitrogen from the fall-applied manure was recovered by tall fescue. This represents a respectable 25-35% of the total manure nitrogen applied in the fall. Surprisingly, 15 kg/ha (13 lb/ac) more nitrogen was recovered from the October application of manure than from the September application.

Fall applied manure improved spring yield of both perennial grasses (tall fescue and orchardgrass) by 1.5-2 t/ha (0.7-0.9 ton/ac) and cover crops (fall rye and Italian ryegrass) by more than 1 t/ha (0.4 ton/ac) (Fig. 21). Yields were slightly better with the October than September applications of manure.  

Fig 21. Yield increase in May crop resulting from application of dairy slurry in the previous fall. (*For Ton/ac multiply by 0.45)

This study shows that it is better to spread manure in the fall on perennial grasses than on fall cover crops and much better than on bare soil. Of the grasses, tall fescue is slightly better than orchardgrass because it is less dormant in the fall.

The benefits of applying manure in fall must be balanced with the associated risks. As the rainy season approaches, the risk of nitrate leaching and surface runoff increases. To minimize risks, manure should not be spread within 10 m (30 ft) of ditches and streams. The Manure Management Guidelines for coastal BC suggest that application rates should not exceed 25% of the annual crop nutrient requirement. Hence, even for perennial grasses, fall manure application should never exceed 120 kg/ha (110 lb/ac) of total N.

Another factor worthy of consideration is the increased risk of disease and winter-kill associated with late fall application of nitrogen. Numerous studies have shown increased susceptibility of grasses to death over winter, or to attack by pathogens, with increasing rates of nitrogen. Ryegrasses are more susceptible to low temperatures than orchardgrass or tall fescue (See Ch. 6).

Phosphorus and Potassium in Manure

Phosphorus in manure is mainly in the organic form and is thus only slowly available to crops. However, organic phosphorus remains available longer because it is less subject to chemical fixation in the soil than soluble fertilizer phosphorus. The net result is that manure applied over many years builds up and maintains available soil phosphorus. Phosphorus is not very mobile in the soil and accumulates over time. Fields with a history of regular manure application usually have adequate phosphorus levels for grass production and do not require additional phosphorus fertilizer.

Phosphorus can be lost to the environment primarily by runoff of organic material or erosion of soil. The key to managing phosphorus for environmental protection is the establishment of good soil conservation practices that reduce runoff and erosion, and to minimize importation of phophorus to the farm.

  Soil Nitrate Tests In Grass Fields - What Do They Tell You?

In recent years, farmers have been encouraged to test nitrate levels in their fields, especially in fall, to obtain a report card on their nitrogen use. High nitrate levels indicate poor nutrient management and warn of potentially high leaching losses over winter.

There is much less risk of high soil nitrate levels in grassland soil than in soil of corn or other annual crops because grasses have a large appetite for nitrogen. A recent trial by Washington State University at Puyallup, WA evaluated different rates and timing of dairy manure application on levels of residual soil nitrate in the fall. In this study, only plots receiving 800 kg of total nitrogen per ha (700 lb/ac) as manure in mid-summer ended up with high levels of soil nitrate in fall (Sullivan, 1997 - unpublished). At Agassiz, applications of 100 kg nitrogen per ha (90 lb/ac) in mid-August resulted in less than 30-35 kg/ha (30 lb/ac) of nitrate-nitrogen in the top 30 cm (12 in) of soil in the fall. These results show that testing soil nitrate levels in the fall can identify forage fields that have been greatly over-supplied with nitrogen.

Because of the importation of large quantities of feed and fertilizer, soil potassium levels have been rising on many dairy farms over the past 15-20 years. Forage grass can take up large amounts of potassium, so elevated soil potassium levels are causing high concentrations in local forage (see Table 6). Excess dietary potassium can cause health problems in cattle (see Pg. 50) but eventually the potassium is excreted in urine.

The potassium in the urine fraction is very soluble. In the soil, it attaches loosely to clay particles and is readily available to plants. Potassium is more mobile in the soil than phosphorus but is less mobile than nitrate. Although some potassium may be leached through soil, especially sandy soil, this is not considered a pollution problem at present.

Rise in levels of soil phosphorus and potassium is a concern on many farms with high livestock densities. Low-density farms may also have problems if more fertilizer is purchased than is required or if excess manure is applied on certain fields. To monitor phosphorus and potassium levels, soil samples should be taken from every field at least every second year. If phosphorus and potassium levels increase without addition of commercial fertilizer, the farm has a manure surplus. In this case, the producer should look for more land or investigate off-farm marketing alternatives for the surplus manure.

Notes From The Underground

1. Invertebrates beneath the canopy

All sorts of invertebrates make their home in the soil: springtails, mites, fly larvae, beetle larvae, millipedes, centipedes, earthworms and many others. Some of these organisms number millions per acre and constitute a considerable biomass. The total weight of earthworms may equal the weight of livestock that can be supported on the land. Some of the organisms, like wireworms and leatherjackets, feed directly on living plant material, but most consume dead organic matter or other soil invertebrates. The soil fauna is important in cycling energy, nitrogen and other nutrients among the various components in the system, including the microorganisms and forage crops.

Manure increases invertebrate populations in forage fields. A trial at PARC (Agassiz) showed that repeated applications of manure increased populations of voracious soil-dwelling insects called 'carabid ground beetles' (Fig. 15 and 16).

 

Fig 16. Carabid beetle populations in soil planted to tall fescue are affected by repeated manure and fertilizer application at PARC (Agassiz), BC

Several species of carabid were found. Fig. 15 shows the relative size of some of the beetles, from 0.3-2.5 cm (0.1-1 in). They are generalist predators that will feed on anything they can handle! Some examples:

-Bembidion species - insect eggs;
-Calathus fuscipes -caterpillars, aphids, weevils;
-Pterostichus melanarius - caterpillars, aphids, weevils;
-Carabus species - insects and earthworms;
-Carabus granulatus - insects, earthworms and slugs.
-P. melanarius appears to be the dominant species in the Agassiz trial. This beetle can eat more than three times its own weight per day. No correlation has yet been made between available food and the carabid populations. In principle, increased carabid populations should reduce the numbers of important pests of forage crops, such as wireworms and leatherjackets, but the overall effect has yet to be determined.

Fig 15. Carabid beetles found in a forage-manure trial at Agassiz, BC. (Photo by J. Troubridge and M.Knott, AAFC).

2. Microscopic creatures of the underworld

Manure contains various 'foodstuffs' (carbohydrates, fatty acids, amino acids, peptides) that provide energy for growth of bacteria and fungi. Therefore, the addition of manure to soil promotes growth of soil microorganisms.

The growing microbes have a great appetite for available nitrogen, from the manure or soil, which they consume and incorporate into their bodies. This nitrogen is 'immobilized' as it is made unavailable for plants or other microbes. The speed of immobilization by microbes is affected by the makeup of the biological community and the conditions in the soil.

Addition of nitrogen fertilizer to nitrogen-deficient soils promotes microbial growth, which temporarily immobilizes some of the fertilizer. Adding manure or other soil additives with high carbon:nitrogen ratios helps to immobilize the nitrogen in the soil.

Two kinds of microscopic animals (microfauna) in the soil graze on the bacteria and fungi that immobilize nitrogen. These are single-cell 'protozoa' and miniature roundworms called 'nematodes'. Although these animals make up less than 10% of the living microorganisms in the soil, they control the populations of bacteria and fungi.

As they feed on microbes and grow, the 'micro-animals' excrete ammonium back into the soil. They also stimulate turnover of the remaining microbial biomass and promote activity of enzymes involved in breaking down nitrogen-containing molecules such as proteins. Release of nitrogen from the living and non-living organic material in the soil is called mineralization.

It is evident that soil 'micro-animals' affect plant growth. In controlled environment studies, plants grown in soil with both microbes and protozoa were able to take up 40-75% more nitrogen than plants grown in soil without the protozoa. Unfortunately, it is difficult to quantify the contribution of the 'micro-animals' to mineralization of nitrogen even when their population is known. Even without protozoa and nematodes, nitrogen in the microbial cells is gradually released as energy sources are depleted and microbes die.

 

Fig 17. Microscopic creatures of the underworld: application of manure and fertilizer produce different effects on populations of soil microbes.

A study at PARC (Agassiz) compared the effects of repeated applications of manure and fertilizer on soil microorganisms under a grass stand. Immediately after the manure was applied, bacteria populations doubled (see Fig. 17). The bacterial growth probably stimulated the short-lived peak of protozoa. The repeated manured plots sustained high populations of bacteria-eating nematodes.

In contrast to manure, nitrogen fertilizer slightly depressed bacteria populations and had no effect on nematodes. In fact, populations of bacteria-feeding nematodes and protozoa were several times greater in manured than in fertilized plots. Interestingly, both manure and fertilizer reduced soil fungi compared to the control.

This study shows that applying manure causes massive unseen changes in soil microbes. The rising bacteria population captures some of the nitrogen that would be available to plants, immobilizing this nitrogen. But the surge of protozoa and the resident populations of bacteria-eating nematodes help to release (mineralize) some of the nitrogen back into the soil. Soils with a history of manure application have a more dynamic response to addition of nutrients than soils that receive only fertilizer. Understanding soil microbes is necessary to predict the fate of nitrogen and other nutrients in the soil.

Contributed by Tom Forge, Lakehill Applied Soil Ecology, Kaledan, BC.

Soil And Plant Analysis - Use A Lab Or Do It Yourself

Dairy farmers in the region submit plant and soil samples for analysis to feed and fertilizer companies and to private laboratories. Analytical procedures vary among laboratories so results are not always comparable. Some laboratories base fertility recommendations on outdated models that do not adequately credit the nutrients in manure or other organic soil amendments. Make sure that the laboratory you are using is current and uses local research to develop its recommendations.

Farmers now have the option of using on-farm quick-tests to do some analyses. On farm kits have several advantages:

Testing is inexpensive. Once the test kit is paid for, each analysis costs much less than a laboratory. Also, the inconvenience and cost of shipping samples is avoided.

Quick results. Results are available within minutes or hours of collecting the sample, depending on the test kit. Commercial laboratories typically have at least 2 - 3 day turnarounds, plus shipping time. Conditions during transportation may affect results.

Accuracy. Some of the test kits now available for soil, plant and manure analysis can produce very accurate results.

Note that because grassland systems are fertilized and manured frequently, an inexpensive reliable quick-test is especially handy for fine-tuning rate of application.

Quick-tests also have some drawbacks:

Consistent results. To get accurate results, the operator must use precise and consistent techniques. When testing samples only 3 or 4 times a year, it can be difficult to maintain identical technique each time.

Complicated procedures. Some test kits require that the user have considerable skill to meticulously follow instructions. While some quick-test kits have proven results under controlled conditions, they may be less effective in on-farm situations. Interpreting the results. Knowing soil nutrient content is of no use unless the results can be used to guide rates of nutrient application. Test kits should be furnished with an interpretation based on local research.

Verification necessary. It is generally recommended that duplicate samples should be periodically sent to a commercial laboratory to verify the performance of the kit.

Fig 22. Nova MKII meter measures ammonium-nitrogen concentration in manure.

Manure Quick-Test Kits

1. The Nova MKII nitrogen meter from Sweden provides a value for the ammonium-N concentration in manure. This test takes less than 10 minutes to complete and is generally accurate to within 10% of laboratory values. (Available from Grass Roots Project Management, PO Box 136, Chilliwack, BC, V2P 6H7)

A measured volume of manure is mixed with a chemical reagent in a sealed container. The reaction releases nitrogen gas, creating pressure in the chamber. A pressure gauge is calibrated to give the ammonium-N concentration in the manure. Where manure application rates are based on ammonium-N, this test kit is adequate.

2.The hydrometer is a cheap and simple tool used to estimate total solids content of manure. (Available from Whatcom Conservation District, 6975 Hannegan Rd., Lynden, WA, 98264)

The hydrometer consists of a glass cylinder with a weighted bottom. It is placed in a bucket of well-mixed manure and allowed to float for 15 sec. Very thick slurry may need to first be diluted. The solids content can be read directly. Calibration charts are used to correlate the solids with nitrogen and phosphorus content. Considering the benefits of diluting thick slurries on crop response (see Fig 7 and 8), the hydrometer is useful for determining how much water to add to reach a desired solids content.

Soil Quick-Test Kits

1. 'NITRACHEK' Reflectometer. This field kit rapidly tests both available ammonium and nitrate content in soil in about one hour. The procedure involves reading paper test strips with a reflectometer. Nutrients are extracted from undried soil with a potassium chloride solution. Adjustments for soil water content are made by means of a standard dilution procedure. This test gives very accurate results, typically within 5% of laboratory values.

2. Nitrate Quick Test. This kit tests only for nitrate-nitrogen and requires that soil samples first be dried at room temperature. Nitrate Quick Test has been found reliable and accurate for Fraser Valley soils with the following qualifiers:

-Nitrate should be extracted with aluminum sulphate rather than potassium chloride. -For soils with low nitrate concentration, a lower dilution should be used (i.e. 2:1 rather than 10:1)

(Hawk Creek Laboratory, Inc. Box 386, Glen Rock PA, 17327)

3. Cardy Meter. This procedure tests for nitrate in soil after air-drying. The dry soil is mixed with an extracting solution and filtered. A few drops of filtered extract are placed on the hand-held nitrate ion meter. Nitrate readings are in parts per million. The bulk density of the soil must be known or estimated to convert to kg/ha (or lb/ac) of nitrate-nitrogen. While not quite as accurate as the Nitrate Quick-Test, the Cardy meter is very simple to use. (Spectrum Technologies, Inc.)

4. N-Trak. The N-Trak test kit is promoted by Iowa State University and used widely in the Midwestern U.S. Soil extract is treated with cadmium and produces a colour reaction depending on nitrate concentration. Nitrate concentration is determined by matching the treated extract with colour chips. This test kit requires subjective colour assessment. Safe disposal of the cadmium reagent must be attended to. The N-Trak is also fairly easy to use.

Crop Indicators

Silage or hay samples are often analyzed for nutritional quality to develop balanced rations for livestock. The crude protein and nitrate information can also be used to assess fertility practices. High protein levels (over 18%) result from short cutting intervals but also suggest very high rates of nitrogen application. High nitrate levels (over 0.1% nitrate-nitrogen) in tissue indicate a possible health hazard for livestock but also suggest excessive application of nitrogen from manure or fertilizer. In general, crude protein levels of 16-18% with nitrate-nitrogen below 0.05% suggest sound nitrogen management, although factors such as variety of grass, stage of growth, weather conditions and time of year need to be taken into account.

A new hand-held instrument called 'SPAD meter' (Minolta Ltd.) is being used in the field to detect nitrogen deficiency in several crops including corn and tobacco. The instrument clips onto a leaf and gives an instant measurement of leaf colour. It detects slight differences in leaf greenness, which is greatly influenced by nitrogen status, although other factors (variety, sulphur, drought, etc) are also involved. This instrument holds promise for use on grass.

Finally, crop response to applied nutrients can be directly evaluated with test strips in the field. Applying more or less fertilizer to strips in a field for comparison is an excellent way to assess the benefit or need for fertilizer. It may be possible to use 'pasture probes' to detect differences in production among the test strips that would go unnoticed visually.

The Value of Manure Analysis and Record-Keeping

Because there is no reliable soil nitrogen test for forage production in this region, producers are encouraged to use the best alternative approach to nitrogen management: establishing a proper record-keeping system. Over time, the records tell a story - they become a report card that shows how well nitrogen and other nutrients are being managed on the farm. Year-to-year variation in weather conditions causes short-term fluctuations in values for the various records, but after three or more years of record keeping, farm trends will emerge. Proper records of nutrient management should contain the following information:

- Soil test results
- Fertilizer applications - time, rate and analysis
- Manure applications - time, rate and manure analysis
- Forage yields (preferably on a dry matter basis)
- Forage analysis (crude protein, potassium, ADF, NDF, moisture)
Large differences in farming operations mean a wide range of nutrient concentrations in manure. Seasonal variation in manure nutrients occurs within farms, particularly those using uncovered storage. Consequently, manure analysis is always recommended. In the first year or two, have the manure analyzed 3-5 times during the growing season. If overall management remains constant and manure analysis results remain consistent from year to year, the frequency of analysis can be reduced.

A computerized system for keeping nutrient records was developed by D. Grusenmeyer and T.N. Cramer of Washington State University Cooperative Extension, Bellingham, WA. Computer diskettes are available from WSU without cost.

Other Nutrients And Lime

Sulphur

Sulphur is an essential nutrient for both plants and animals. Many compounds in plants and animals contain sulphur, but most important are the sulphur-containing amino acids (i.e., methionine, cystine and cysteine). Since amino acids also contain nitrogen, there is a close association between nitrogen and sulphur content in both plants and animals. The ratio of N:S in plants and animals is approximately 15:1, varying more widely in plants than in animals. Plant sulphur concentrations typically range from 0.15 - 0.30%. A 13 tonne/ha (6.0 ton/ac) grass crop takes up about 20 kg/ha (18 lb/ac) of sulphur compared to 250-400 kg/ha (225-360lb/ac) of nitrogen and 45 kg /ha (40 lb/ac) of phosphorus.

Sulphur in Soils of Southern BC and the Pacific Northwest

Total sulphur content of the surface horizon of soils ranges a thousand-fold (50-50,000 ppm or 0.005-5%). The organic form makes up 90-98% of the sulphur in the surface horizon of most agricultural soils. The most abundant inorganic form of sulphur in well-aerated soils is sulphate. Most sulphate, especially in acid soils, is bound or adsorbed to the mineral fraction of the soil while some sulphate is dissolved in soil water. Plants take up sulphur more readily in the inorganic sulphate than organic sulphur form.

Responses by forage crops to applications of sulphur have been documented from the humid to the arid regions of the Pacific Northwest. In the lower Fraser Valley, responses of forages to sulphur application have varied from substantial increase in yield to no effect; in one study yield actually decreased. Spring and fall harvests tend to respond more than those in mid-summer. Response is usually greater by legumes than grasses, so sulphur applications can help to maintain clover in mixed stands.

Soil Testing for Sulphur

Although commercial laboratories routinely analyze soil for sulphur, the effectiveness of the tests is not known. The chemical solutions for extracting available sulphur have not been standardized, adding to the difficulty of comparing and interpreting the results.

Soil testing solutions generally extract most of both organic and inorganic sulphur fractions and no allowance is made that plants take up sulphur more readily as inorganic sulphate. Also, soil tests cannot make allowance for the mineralization of organic sulphur to sulphate by microbes during the growing season.

Fertilizing with Sulphur

It is tempting to regularly apply sulphur fertilizer as an "insurance" for maximum yield because the soil test is uncertain and because sulphur fertilizer is inexpensive. Sulphur can be easily included in fertilizer blends, especially with certain nitrogen, phosphorus, potassium and magnesium fertilizer formulations. Recommended application rates for sulphur in British Columbia are modest, ranging from 10 - 35 kg/ha (9-32 lb/ac).

However, there are some detrimental consequences (besides the extra cost) to applying sulphur in excess of plant requirements. Most sulphur fertilizers acidify the soil so additional lime is required to counteract this effect. In some cases, reduced yields have resulted from even low rates of sulphur application. Finally, sulphur is known to reduce the uptake of other nutrients. For example, sulphur and selenium behave quite similarly in the soil, and sulphur applications have been shown to reduce selenium concentration of forages. This could exacerbate situations where low selenium in feed is already a livestock health problem (see Pg. 51). Sulphur may also contribute to an imbalance of copper and molybdenum in ruminants.

There are numerous options for adding sulphur as commercial fertilizer. The least costly source is 'elemental sulphur' which contains 95-99% sulphur. Unfortunately, elemental sulphur is unavailable to crops until it is oxidized to sulphate by soil microorganisms. Oxidation rates vary greatly among soils. As there is little information on oxidation rates for coastal soils, it is best to consider elemental sulphur as a "slow-release" form of fertilizer.

Some primary fertilizers contain sulphur in the available sulphate form. For example, some nitrogen fertilizers (e.g. 16-20-0 and 21-0-0) contain substantial proportions of sulphur while the formulation 34-0-0 can contain either substantial sulphur (sulphur coated urea) or almost none (ammonium nitrate). Phosphorus fertilizers such as 0-18-0 and 0-46-0 can contain up to 12% sulphur, depending on their geological source and degree of refinement during manufacturing. The potassium fertilizer 0-0-50 contains about 18% sulphur. The fertilizer called 'SulPoMag' (sulphate of potash-magnesia) is a popular source of magnesium that contains about 22% sulphur. The lime source, gypsum (calcium sulphate), contains 16% sulphur.

All organic wastes, including manure, contain some sulphur primarily in the organic form. Four years of manure application has significantly increased sulphur level in the surface horizon at PARC (Agassiz). There is little information on the availability of sulphur from organic sources but it is assumed that they would be more slowly available than inorganic sulphate.

It should be remembered that sulphur from atmospheric pollution is deposited on soils via precipitation. The amount of deposition depends on the amount of industrial activity, especially the amount and quality of coal that is being burned. As pollution is reduced, more sulphur fertilizer is needed. A few measurements taken at PARC (Agassiz) showed low sulphur concentrations in rainwater so that the annual contribution from rain would be only about 5 kg /ha (4.5 lb/ac). Sea spray contributes sulphur within a few kilometres of the ocean. Sulphur may also be present in irrigation water.

-'Sulphur' contributed by C.G.Kowalenko, PARC (Agassiz)

Table12. Function and requirements of micro-nutrients by forage in BC and the PNW

Micro-Nutrient Plant Function Requirement
Aluminum Toxic to plants Aluminum is a trace mineral that reduces crop growth by either accumulating in toxic quantities in the plant or by influencing other nutrients. Research has shown that aluminum toxicity occurs on acid soils in south-coastal BC Liming effectively reduces availability of aluminum.
Boron Function in plants is not well understood. Deficiency shows up as failure of root tips to elongate normally Cell division in shoot apex is also inhibited. Boron deficiency is widely reported in south-coastal BC Considerable work on plant tissue analysis has been conducted but results are not conclusive enough to develop reliable recommendations. Soil testing appears to be the best method for predicting boron fertilizer requirements but there is a shortage of field data to interpret soil test results. Grasses are classified as having low boron requirements relative to other plants. There is a tendency for manure to increase soil boron.
Chlorine Stimulates the splitting of water during photosynthesis; also essential for roots and cell division in leaves. Leaf deficiency symptoms consist of reduced growth, wilting and development of chlorotic or necrotic spots. Research is insufficient to draw conclusions about the chlorine status of BC soils. Chlorine concentrations are generally high near salt water and lower further inland. Chlorine has been shown to enhance disease resistance in plants.
Cobalt Not required for plants. Cobalt has not been examined extensively in BC soils. Animal deficiencies can be easily treated with mineral supplements.
Copper Copper is present in several enzymes or proteins involved in oxidation and reduction processes. In deficient plants, young leaves often become dark green and twisted or otherwise mis-shapen. Plant and soil analyses indicate variable levels of copper in south-coastal BC, ranging from deficient to adequate. The relationship of these analyses to crop growth has not been clearly defined for this region. In one greenhouse study, copper application to forage did not increase yield but did rise copper concentrations in plant tissue. Often the supply of copper is adequate for plant but not livestock needs so copper has to be given to livestock.
Iron Required in fundamental electron transport processes. Deficiency shows up as chlorosis between the veins of youngest leaves. Iron is not generally limiting in forages in south-coastal BC. Availability of iron decreases with increasing pH. Little research has been directed at developing methods for predicting iron deficiency or solving problems if they occur .
Manganese Plays a structural role in the chloroplast membranes; also involved in the photosynthetic reaction that splits water . Deficiency appears as chlorosis between veins of young and old leaves and necrotic lesions. Both deficient and toxic soil conditions exist in south-coastal BC. Manganese requirements are influenced by crop, soil and weather conditions. Manganese availability decreases as pH increases so manganese fertilizer recommendations must take into account pH. Manure tends to decrease available manganese.
Molybdenum Function in plants is not well understood - part of the enzyme "Onitrate reductase" that reduces nitrate to nitrite. Deficiency appears as chlorosis between veins of first (oldest) leaves and progressing to youngest. Research in south-coastal BC has been insufficient to determine whether molybdenum is adequate for general crop yield and crop quality for animal production. Molybdenum interferes with copper metabolism in cows .
Selenium Not required. It is well-established that forages in coastal BC have inadequate selenium for livestock needs. Research at PARC (Agassiz) has demonstrated the possibility of using a slow-release selenium fertilizer to supplement forages (see below).
Zinc Required to produce the hormone indoleacetic acid that regulates growth. Also contained in many enzymes. Deficient plants show reduction of growth in young leaves and stems. Response to zinc fertilization in BC has been variable. The availability of zinc decreases as pH increases so fertilizer recommendations must take into account management practices, particularly liming, that alter pH . Zinc toxicity may occur on acidic soils or from excessive zinc applications. Zinc is generally low in animal feeds in BC but low levels have not impacted reproduction or overall performance of animals. Manure application tends to increase available soil zinc.
(Summarized from Kowalenko, C.G. and Neilsen, G. 1992. Assessment of the need for micronutrient applications for agricultural crop production in British Columbia. Agriculture and Agri-Food Canada Technical Publication.)

Effect Of Dairy Manure On Soil Attributes

Soil Character Effect Of Manure
Calcium Increase
Potassium Increase
Magnesium Increase
Phosphorus Increase
Sodium Increase
Sulphur Increase
Copper Slight increase
Iron Slight decrease
Manganese Decrease
Zinc Increase
Boron Slight increase
Conductivity Increase
pH Increase (compared to fertlizer)

Micronutrients

Micronutrient requirements of forages have been studied sporadically for many years in BC and the PNW. Use of micronutrient fertilizers has generally increased over the years. Micronutrient deficiencies may affect plant growth or animal performance. Certain micronutrients (copper, zinc, manganese, iron and molybdenum) are required in greater concentration by animals than by plants while others (cobalt and selenium) are required by animals but not by plants. Table 12 summarizes the current state of understanding of micronutrient needs for forages in coastal BC and the PNW. Adding Lime

Soil acidity often reduces pasture production in coastal BC and the PNW. Acidity of soils can be reduced by spreading lime. Lime applied to the soil surface of long-term grass stands does not readily soak into the soil. Instead, mixing of lime through the soil profile is accomplished by the soil-dwelling organisms, particularly earthworms.

A recent trial investigated the rate of mixing of surface-applied lime and effect on crop response in four orchardgrass and ryegrass pastures in western Oregon. Lime was applied in the fall of 1993 at 0, 2.5 or 5 t/ha (0, 1.1 and 2.2 ton/ac). In 1994, no effects were detected on production, plant nutrient content, lime mixing or soil nutrient content. By 1995, two of the four sites displayed increased soil pH and calcium levels to a depth of 10 cm (4 in) while the other two sites had mixing to 5 cm (2 in).

Lime increased production in two pastures by 0.5 t/ha and 1.7 t/ha (0.3 and 0.9 ton/ac). In one of these pastures, the lime was mixed to only 5 cm (2 in) depth, suggesting that shallow mixing may be adequate to stimulate production.

The same factors that regulate earthworm activity also regulate lime movement: temperature, moisture and soil textural class. The depth to which lime mixing occurs is the depth to which soil acidity (pH) is affected.

Soil pH affects the availability of several nutrients. Listed below are some of the benefits of liming on nutrient availability and soil properties:

-Lime increases phosphorus availability by reducing solubility of aluminum and iron. In acid soils, aluminum and iron dissolve somewhat and bind to phosphorus in solution, making it unavailable.

-Lime increases nitrogen and organic matter by creating a more hospitable environment for soil fauna (i.e. earthworms) and microbes, which results in greater decomposition of soil organic matter and higher rates of nitrogen mineralization. Lime particularly favours the conversion of ammonia to nitrate (nitrification).

-Lime reduces levels of soluble aluminum that may be phytotoxic.

-Lime reduces manganese levels that may be phytotoxic.

In the Oregon study, liming increased production by stimulating mineralization and nitrification. Lime increased uptake of nitrogen by grasses in the two responsive sites by 55 and 85 kg/ha (50 and80 lb/ac). Both pastures had received 125 kg/ha (110 lb/ac) of inorganic nitrogen fertilizer.

The responsive sites contained higher organic matter in their surface layer (2.5 cm or 1 inch deep) than the unresponsive sites. The organic matter is a source of nitrogen for mineralization/nitrification which can lead to increased production. However, high organic matter may also indicate a thatch buildup due to acidity. Thatch may reduce uptake of nitrogen fertilizer due to a high C:N ratio and perhaps due to its effect on plant root distribution.

-'Adding Lime' based on J. Rogers, 1995. "Effect of top-dressed lime upon pasture production and quality," M.Sc. Thesis (Oregon State University).

Nutrients And Feed Quality

Nitrates in Forage

Where do nitrates come from? Plants can absorb nitrogen from the soil in only two forms, nitrate and ammonium. Ammonium in the soil, originating from manure, fertilizer or soil organic matter, is easily converted to nitrate by specialized bacteria (see 'Nutrient Cycle,' Pg. 24).

Nitrate moves freely in the soil but in cold soils, forages take up more ammonium than nitrate. High levels of ammonium can actually be toxic to plants but ammonium is rapidly converted to amino acids in leaves. In contrast, nitrate is first converted to ammonium, which is then assimilated into proteins.

Research at PARC (Agassiz) has shown that more than 10% of plant nitrogen can be in the nitrate form, although in extreme cases values of 50% have been reported. Rapidly growing leaves require 0.05-0.15% nitrate-nitrogen so concentrations in the entire plant greater than 0.1% indicates that excessive nitrogen has been supplied.

Fig 23. Relationship between crude protein and nitrate-nitrogen in four harvests in coastal BC.

Factors causing nitrate accumulation

Conversion of nitrate to ammonium involves removing oxygen atoms. The process is called reduction, which is the opposite of oxidation. This reaction is very energy demanding, consuming half of all the energy used by plants for growth.

Nitrates accumulate in plants when the rate of uptake is greater than the rate of reduction to ammonium. The rate of reduction is limited by the amount of energy available from photosynthesis.

Factors that restrict photosynthesis more than uptake of nitrate cause nitrate accumulation. Defoliation obviously reduces photosynthesis, so initial regrowth after harvest is typically high in nitrate. Maximum nitrate concentrations typically occur about two weeks after application of fertilizer, depending on environmental conditions. Therefore, delaying application of fertilizer or manure tends to increase nitrate at harvest. Nitrates are highest in grasses harvested before the heading stage.

Low light levels also increase nitrate levels. It has been suggested that grass suspected of having high levels of nitrate be harvested in late afternoon to reduce concentrations. Low temperatures reduce uptake more than photosynthesis, hence decrease nitrate. Sudden drought under high summer temperatures, or sudden frost, can cause plants to accumulate dangerously high levels of nitrate.

Fig 24. Effect of applying 400 kg/ha (360 lb/ac) of nitrogen fertilizer on nitrate levels in forage grasses. The fertilizer was applied in different seasonal distribution patterns.

Forages differ in their tendency to accumulate nitrate. Nitrate accumulators include orchardgrass, tall fescue, many broadleaf weeds and annual crops such as Italian ryegrass, sorghum-sudangrass, fodder rape, cereals other than wheat and root crops such as beets. Other grasses, such as smooth bromegrass, timothy and perennial ryegrass, have a lesser tendency to accumulate nitrate. Legume crops accumulate least nitrate because they assimilate protein in the roots rather than leaves.

Studies at PARC (Agassiz) have shown that the tendency to accumulate nitrate in grasses varies with the season. In spring and autumn, crude protein reaches 16% with safe levels of nitrate, but in summer dangerous levels are reached below 15% crude protein (Fig. 23). Producers often strive for protein levels well above 16%. Perhaps nitrate levels above 1700 ppm (0.17%) can be taken as a report-card indication of excessive nitrogen application.

Table 13: Critical nitrate-toxicity levels to cattle as affected by crop usage.

Nitrate-N

Concentration

Feed Class

Safe for all forages
>0.17% Potentially toxic as conserved forage
>0.34% Potentially toxic as green-feed
>0.45% Potentially toxic to grazing cattle.

With uniform applications of 100 kg/ha (90 lb/ac) of nitrogen for each harvest, nitrate levels stay near the hazard line (Fig. 24). Applying most of the fertilizer in the spring increases the nitrate risk for the first and second harvests. Note that after heavy spring applications of nitrogen, the risk of high nitrate persists late into the season, probably because the nitrogen is temporarily immobilized by soil organisms.

Effect of high nitrate

Nitrate, unlike ammonium, is not toxic to plants. However in animals, nitrate is converted to nitrite, which interferes with the ability of the blood to transport oxygen, causing reduced blood pressure, heartbeat and respiration. In acute cases, livestock may die very quickly following the consumption of high-nitrate feed. Chronic exposure to high levels of nitrate may interfere with vitamin A and iodine metabolism causing reduced milk production and higher incidence of abortion.

The toxicity level for nitrates differs with the source of feed because the rate of nitrate release varies (Table 13).

Tips to Minimize Risk of Nitrate Poisoning

  • Do not feed forage grown under drought, low light levels, high nutrient loading or premature frost without analyzing for nitrates.
  • Preserve high-risk forages as silage, not as hay. The ensiling process reduces nitrate levels by over 50%.
  • Change feeds gradually, especially when the new feed is suspected of containing nitrates. Changes in feed programs that alter rumen function or bacterial population will increase susceptibility to nitrate toxicity.
  • Mix (dilute) high-nitrate forages with low-nitrate feeds.
  • Provide a well-balanced feed program. Healthy animals on balanced rations are better able to tolerate nitrates than under-fed animals. Feed sufficient levels of energy, protein, more minerals (including trace elements) and Vitamin A.
  • The highest level of nitrate in the plant is in the base of the stem or stalk. Therefore, cut silage corn that has been subjected to drought high above the ground.
  • Test your water supply for nitrates
  • If you suspect a case of nitrate toxicity, contact your veterinarian immediately. Note that nitrate toxicity symptoms are similar to those of other management or disease problems. Also, consult with your farm advisor and have your feed analyzed.

(Based on G Smith, 1990, Dairy Producers Short Course)

Potassium - Too much can really stun your dry cows!

A high level of soil potassium can have a serious impact on health of cattle. Grasses and alfalfa are luxury consumers of potassium, meaning that the more potassium in the soil, the higher the concentration in the plants.

Excess potassium in the diet (over 3.5%) reduces absorption of calcium and magnesium in the digestive tract of cows. High concentrations of potassium relative to calcium and magnesium in the feed cause a wide array of metabolic disorders such as milk fever, calving problems and displaced abomasums.

Dry cows are most susceptible to high potassium and, to make matters worse, these cows are usually fed the greatest amount of home-grown forage. Although lactating cows are less sensitive, research at PARC (Agassiz) found that cows fed forage with 4.6% potassium had higher water intake and triple the urine output of cows fed forage with 1.6% potassium. High urine output indicates that the kidneys are working overtime and that could have long-term implications for the health of the cow.

Table 14: Content of potassium, magnesium, and calcium in forage grasses.

(Mg)

Magnesium

(K)

Potassium

(Ca)

Calcium

Mg/K Mg/(K+Ca)
Tall fescue 0.35 2.67 0.58 0.130 0.107
Meadow fescue 0.27 2.75 0.70 0.099 0.079
Orchardgrass 0.23 2.95 0.57 0.079 0.066
Perennial ryegrass 0.19 3.21 0.67 0.060 0.050

What to do about high potassium in forage?

Potassium builds up in soils of high-density livestock farms because the quantity of potassium coming onto the farm, mostly in feed, exceeds the quantity leaving the farm in milk and meat. There is no easy way to circumvent potassium accumulation, but several management steps are available to minimize the harmful effects:

I. REDUCE POTASSIUM CONTENT IN FORAGES

1. Reduce potassium fertilizer application and eliminate off-farm manure sources.

2. Set aside a specific field (5-10% of land-base) for feeding dry cows. This field should receive mostly mineral fertilizer (no K) and little manure. Over time, the forage grown on that field should decline in potassium. In a recent study at PARC (Agassiz), soil potassium levels in a tall fescue stand dropped by 45% (88 ppm) after 3 years of fertilizer application (high rates of nitrogen and moderate rates of phosphorus and potassium). In contrast, soil potassium increased dramatically in areas receiving high rates of manure for 3 years.

Note that a large crop removes more potassium from the soil than a small crop and that potassium concentration is more dilute in heavy forage crops.

3. Dilute high potassium forages with low potassium feeds. Warm-season grasses (e.g. corn) usually have lower potassium levels. Corn stalks are especially low in potassium. Purchased forages and commodities (i.e. cottonseed, brewers grain) obtained from non-livestock farms are usually low in potassium.

Note that increasing purchased feed will add to the potassium loading on the farm unless the manure is exported off the farm.

II. ENHANCE MAGNESIUM CONTENT

1. Use grasses that are naturally high in magnesium (high Mg/(Ca+K)) such as tall fescue (see Table 14) for feeding dry cows.

2. Look for new varieties that may be released in the future with improved balance of magnesium to potassium plus calcium. Unfortunately, there is little likelihood of new varieties that can exclude potassium.

3. Fertilize with magnesium oxide or dolomitic limestone. Tall fescue removes the most magnesium hence requires the greatest supplement. Avoid SulPoMag fertilizer because of the potassium content.

4. Consider adding magnesium oxide and anionic salts to the diet of close-up cows. Unfortunately, these additives are not very palatable and developing an appropriate diet is difficult.

Table 15: How to determine if your farm is deficient in Selenium.
Test Deficient Marginal Adequate
Soil Less than 300 ppb 300-500 ppb More than 500 ppb
Plant Less than 100 ppb 100-200 ppb More than 200 ppb
Whole Blood Less than 10 ppb 10-20 ppb More than 20 ppb

Selenium 'Fertilizer'

Livestock fed crops grown on selenium-deficient soils, such as in coastal BC and the PNW, must be provided with this essential trace nutrient. Symptoms of selenium deficiency include white muscle disease, infertility and poor growth. Selenium is currently administered to ruminants in feed supplements, mineral licks or by injections, but these methods are expensive or difficult to manage. Applying selenium as a fertilizer to raise the level in the grass is widely practised on New Zealand pasture land.

Fig 25. Slow-release selenium (Selcote Ultra) enhances selenium in forages for an entire year at PARC (Agassiz). (Note: 10 g/ha is equal to 0.02 lb/ac).

Selenium is difficult to apply as a fertilizer because the rates required are extremely low. Soluble selenium can be applied with pesticide sprayers but the effectiveness is short-lived. In New Zealand, farmers are using a new slow-release selenium product called Selcote Ultra. This prilled product can be blended with other fertilizers to facilitate application. Research at PARC (Agassiz) showed that just 10 g/ha (0.02 lb/ac) of selenium (as Selcote Ultra) applied in spring raised levels of selenium in the forage for an entire year. In contrast, soluble selenium was ineffective after a few months (Fig. 25).

Producers should check with suppliers for availability and regulations regarding use of any selenium fertilizer. Treated forage should always be monitored.

Chapter 6: Rise and Decline of Forage Stands

Raising New Forage Stands

When you plant orchardgrass seed at 35 kg/ha (30 lb/ac), you are planting over 5000 viable seeds per square meter (500 seeds per sq. ft). With good seeding technique (firm seedbed, shallow seeding depth), warm soil and moisture, over 80% of these seeds typically emerge. However, within three years, 90% of the emerged plants die off while the surviving plants grow and occupy an increasing amount of space, a process referred to as self-thinning.

The seed of even improved and registered forage varieties is genetically variable. This is because the flowers of most forage species (both grasses and legumes) are fertilized by cross-pollination. The pollen of grasses is carried by wind and the pollen of legumes is carried by insect pollinators. Cross-pollination mixes the genes and creates genetic diversity.

In contrast, breeders can produce genetically uniform seed of most cereals because these crops self-pollinate. Corn seed is also genetically uniform because pollination can be easily controlled.

In the self-thinning process the hardiest individuals in the population (not necessarily the highest yielding) prevail. As some plants die off, survivors expand to fill the space. This process is gradual and almost invisible as dead plants are rarely seen!

When different forage species are sown together, those that produce vigorous seedlings generally dominate. Several forage grasses ranked in order of seedling vigour and seed size are listed in Table 1. Note that the large-seeded grasses are not always the most vigorous. However, small seed must be planted no deeper than 1 cm (0.5 in) whereas the larger seed will emerge from 2.5cm (1 in) depth.

Grasses differ from one another in how they expand to occupy available space. Tall bunchgrasses (explained in Ch. 1), such as orchardgrass, timothy and Matua prairiegrass, increase the size of individual plants by producing larger and more numerous tillers. Perennial ryegrass produces relatively small tillers but each plant can produce a great many tillers, resulting in very dense stands. Tetraploid varieties of both Italian and perennial ryegrass produce fewer but larger tillers than diploid varieties. Tall fescue plants spread by short underground stems, called rhizomes, gradually producing a dense sod. Quackgrass, smooth bromegrass and Kentucky bluegrass produce vigorous rhizomes that enable the plants to spread rapidly. White clover spreads by above-ground prostrate stems called stolons. Note that the taller grasses can compensate for low plant density by producing very large tillers so that even relatively thin stands can sometimes produce high yields, provided that weeds are kept out.

Table 2. Effect of establishment method on yield of perennial ryegrass and orchardgrass at PARC in south-coastal BC.
Establishment Method Yield (Dry Matter)

t/ha (T/ac)

Establishment Year Second Year
Barley 'Nurse' crop 8.1 (3.6) 11.9 (5.4)
Oats 'Nurse' crop 8.0 (3.6) 11.9 (5.4)
Weedy 7.3 (3.1) 12.1 (5.5)
Herbicide 7.1 (3.1) 11.9 (5.4)

Seeding with 'nurse' crops

A newly cultivated field is an ecological vacuum. The plants best adapted to invade are the fast-establishing annual weeds. These weeds can threaten the establishment of the more sluggish perennial forages. Before herbicides were widely available, farmers seeded perennial forages with faster-growing cereals, calling them 'nurse crops' because they kept weeds out. Although the cereals also compete with forage seedlings, cereals are more useful and manageable than weeds.

A study was conducted at PARC (Agassiz) to compare three methods of controlling weeds during establishment of orchardgrass and perennial rye-grass. The study compared barley and oat 'nurse' crops, herbicides and mowing.

The results showed that, under our moist maritime conditions, seeding with 'nurse' crops provided more forage and crude protein in the year of establishment than using herbicides or mowing (see Table 2). Indeed, there was no advantage to using herbicides for weed control and, of course, no herbicides are available for controlling annual grassy weeds in forage grasses (see Ch. 4). All establishment methods produced the same amount of forage in the second year. Note that seeding tall fescue with a 'nurse' crop may be risky because of the slow early growth of this grass.

Some farmers in the region have had success including a small amount of relatively short-lived perennial ryegrass (up to 20% of seed mix) as a 'nurse' crop for longer-lived orchardgrass and tall fescue. Sod-seeding perennial ryegrass in spring into fall-seeded orchardgrass or tall fescue has also been successful for some producers.

Which Forage Maintain Production Best?

Fig 1. A trial to compare grasses at PARC (Agassiz) in south-coastal BC.

Some locally grown forages can maintain their production for many years, even when density of the stand has declined somewhat. A study at PARC (Agassiz) compared production of new (1-3 year-old) and old (5-7 year-old) stands of several grass varieties in the same time period (1993-1995) (see Table 3). The study showed that for tall fescue, yield of old and new stands was equivalent. Yield of older stands of orchardgrass had declined by about 1.0 t/ha (0.5 T/ac.). Interestingly, the stand density of Hallmark or chardgrass had declined substantially due to infection by cocksfoot mottle virus (see below) but the yield decline was small. Few weeds had invaded the orchardgrass. Timothy and meadow bromegrass also maintained production well. Several grasses, most notably perennial ryegrass, yielded very poorly after three years.

Another study at PARC (Agassiz) showed that applying high doses of dairy slurry for several years reduced stand density of tall fescue. Nevertheless, yield of the heavily fertilized stands remained very high. These observations suggest that high rates of nutrient application increase size of individual plants, causing more competition for light and ultimately enhancing the self-thinning process.

Table 3. Comparison of yield of young (average of year 1-3) and old (average of year 5-7) stands of several grass speices and cultivars grown in coastal BC in 1993-95. Note: where no values are shown, sward had greatly declined and yield was not measured.
Species Cultivar Annual Yield

(t dry matter /ha)*

Young Old Difference
Persistent Grasses
Orchardgrass Hallmark 14.5 13.4 -1.1
Orchardgrass Prairial 14.6 13.7 -.09
Orchardgrass Mobite 13.0 12.2 -0.8
Tall fescue Johnstone 13.7 14.0 0.3
Meadow fescue Bundi 10.9 10.2 -0.7
Timothy Toro 14.9 14.0 -0.9
Meadow bromegrass Regar 14.5 13.1 -1.4
Non-Persistent Grasses
Prairiegrass Grassland Matua 13.7 - -
Reed canarygrass Palaton 12.5 - -
Perennial ryegrass (2N)** Frances 11.4 - -
Perennial ryegrass (4N)** Bastion 10.9 - -
Perennial ryegrass (4N)** Condesa 10.9 - -
Perennial ryegrass (2N)** Melle 10.7 - -
Sweet bromegrass Deborah - - -
Bromus sitchensis Grassland Hakari - - -
Smooth bromegrass Manchar - - -
* for T/ac multiply by 0.45 **2N=diploid, 4N= tetraploid

Short Term and Long Term Productivity of Forage Grasses in Coastal BC

Productivity Of New Stands Productivity Of Older Stands
  • Highest yielding grasses were timothy, orchardgrass (early and medium maturing varieties), and meadow bromegrass.
  • Tall fescue, reed canarygrass and 'Matua' prairie grass yielded 1 t/ha less than the top grasses.
  • Perennial ryegrasses (both diploid and tetraploid) and meadow fescue yielded 3 t/ha less than the top grasses.
  • Three of the grasses were invaded by weeds within the first 3 years.
  • Productivity of older stands. Tall fescue maintained its production best; yield in years 5-7 equaled years 1-3.
  • Yield of the other persistent grasses (orchardgrass, timothy, meadow bromegrass) declined by about 1 t/ha in the older stands.
  • Several grasses did not persist past 3 harvest years due to winter kill and other factors, including perennial ryegrass, 'Matua' prairiegrass, and reed canarygrass. Less winter kill is expected near the coast.
  • Meadow fescue had mediocre yield but excellent persistence.

Grasses And White Clover

White clover and other legumes are often seeded with grasses because they contribute nitrogen through fixation and because of their high nutritional quality. The use of white clover in forage fields that have high nitrogen inputs has declined partly because the clover does not persist in the sward.

A study was conducted by PARC (Agassiz) to determine which grasses are most compatible in mixed stands with Ladino white clover (large type) under high inputs of nutrients. These stands received 375 kg/ha (350 lb/ac) of nitrogen annually.

The study showed that clover cannot compete with orchardgrass because of shading (see Table 4). Three varieties of orchardgrass were tested with similar results. White clover produced well when planted with the other grasses, especially with tall fescue, despite the large input of nitrogen. Some farmers are concerned that white clover competes aggressively with tall fescue causing the grass to die out. It is more likely that the clover invades patches with poor grass growth. The decline in white clover between 1990 and 1991 was due to severe winter conditions that also killed the perennial ryegrass (see 'Winter injury,' p.78).

An unexpected result in this study was that the grasses growing with the clover often looked more robust than the grass growing in a pure stand. Also, the overall yield of the mixtures was often greater than that of the pure stands. In recent years, peas and other annual legumeshave been shown to benefit cereal crops grown in rotation beyond their contribution of fixed nitrogen. Can this be a similar phenomenon?

Table 4. The proportion of clover harvested in heavily fertilized grass-clover mixtures at PARC (Agassiz).
Clover Harvested In Grass-Clover Mixtures

(% clover by dry weight)
1989 1990 1991 1992
Orchardgrass 1.9 1.6 1.4 0.3
Tall fescue 25.4 17.8 3.9 4.4
Timothy 10.3 18.4 2.1 2.8
Perennial ryegrass 20.7 31.6 - -

Response To Irrigation

Forage production in coastal regions of BC and the Pacific Northwest is vulnerable to summer drought for two reasons. Abundant precipitation through much of the year and frequent high water tables limit rooting depth. Also, many of the best forage fields have coarse-textured soils that dry out quickly. For these reasons and the typical mid-summer drought in the region, farmers can expect to increase forage yield by 2-3 t dry matter/ ha (1-1.5 T/ac.) with summertime irrigation (see Table 5). Even greater response to irrigation can be expected in areas with particularly low summertime precipitation such as southern Vancouver Island.

Perennial ryegrass and timothy produce very poorly in mid-summer, particularly in dry conditions. These grasses have relatively shallow root systems. In contrast, orchardgrass and tall fescue have deeper roots and better summer growth. It is somewhat surprising that irrigation does not favour the shallow-rooted grasses more than the deep-rooted ones. The likely explanation is that summertime yield reduction in grasses is due to high temperatures as well as to water deficits.

Table 5. Effect of summertime irrigation on dry matter yield of several grass speices at PARC (Agassiz) (1989-90).
Species Variety No Irrig. Irrig. Increase
   
t/ha *
%
Orchardgrass Hallmark 15.0 17.7 17.7
Prairial 13.8 15.5 12.7
Mobite 11.5 14.8 28.8
Tall fescue Johnstone 13.4 16.4 22.4
Perennial ryegrass Frances 10.0 11.7 17.1
  Mell 8.9 11.0 23.6
  Bastion 9.2 12.5 35.3
  Condesa 9.7 11.8 22.3
Reed canarygrass Palaton 10.5 13.3 27.3
Meadow bromegrass Regar 12.5 14.5 16.1
*For T/ac multiply by 0.45

Orchardgrass And Tall Fescue

The list on the next page compares tall fescue and orchardgrass and shows that both grasses have valuable attributes not found in the other. By using both species, farmers can diversify their forage crops thereby improving production and reducing risk.

Table 6. Comparison of Tall Fescue and Orchardgrass.
Tall Fescue Orchardgrass
Seedling
Establishment Slow Moderate
Competitiveness with weeds Poor Moderate
Seeding rate 35-40 kg/ha 25-30 kg/ha
Adaptation
Flooding Good Moderate
Drought Good Good
Winter hardiness (adapted varieties) Very Good Good (var. Kay=superior)
Grazing suitability Very Good Good
Sod strength for supporting traffic Very Good Good
Performance
Yield Up to 2 t/ha more than orchardgrass
Maturity range of varieties Apr 23 - May 10 May 7 - 28
Rate of drying or wilting Very Good Good
Fall growth Very Good Good
Persistence Excellent Good
Disease Resistance
Stripe Rust Resistant Susceptible
Crown Rust Susceptible Resistant
Leaf Scald Resistant Susceptible
Cocksfoot Mottle Virus Resistant Susceptible
Nutritional Quality
Milk Yield Very Good Very Good
Feed Intake Good-Very Good Very Good
Endophyte * No** No
Alkaloids * Low ** No
* See Fescue Endophyte Story in Chapter 7 ** Registered seed of improved varieties.

Decline Of Forage Stands - Why It Happens

Table 6. Tiller death due to frequent defoliation.
% tiller death
Orchardgrass 4
Tall fescue 16
Timothy 31

After five or six years, self-thinning slows down and grass populations tend to become stable. However, many environmental stresses continue to act on the plant community so that stands may continue to deteriorate.

Frequent defoliation reduces plant vigour and contributes to death of tillers. Table 6 compares the grazing tolerance of grasses. Orchardgrass withstands frequent clipping or grazing because it conserves root reserves and can re-grow from cut tillers. Timothy is known to be susceptible to frequent clipping, especially during stem elongation, because it does not conserve nutrients and produces few new tiller buds during this growth stage.

Fig 2. Severe winter conditions caused great stand losses in 1990-91

The best strategy to withstand frequent clipping is to maintain growing points beneath the grazing height to ensure that they are not removed. In short grasses, like perennial ryegrass and Kentucky bluegrass, defoliation encourages tillering, which promotes a thick sod and high productivity. The thick sod maintains sufficient leaf cover for trapping sunlight even when the grass is grazed short. This approach would not work as well for taller species like timothy or orchardgrass with elevated growing points. Tall fescue is probably intermediate in this respect.

Perhaps related to this is the depth of rooting. Grasses with short leaves and rapid tillering tend to have shallow roots while tall and upright grasses have deeper roots. Short grasses such as perennial ryegrass, bluegrasses and fine-leafed fescues have dense roots near the soil surface. Many tall grasses with deeper rootssurvive and even grow through dry spells by drawing on water deep in the soil.

Fig 3. Winter kill - variety differences.

Winter injury: learning from the winter of 1990-91

Winter conditions in the region are usually moderate so severe damage to forage varieties is unusual. In some years winter injury occurs but goes unnoticed because it results only in delayed spring growth that may be attributed to other factors. However, in the winter of 1990-91, forage crops all over coastal BC and Northwest Washington were decimated. Less damage occurred near the coast.

What causes winter-injury to plants? Low temperature is not the only factor. For example, alfalfa is likely to persist longer near Winnipeg or Saskatoon than it does in this region. Wet soils, high water table, frost heaving, desiccation, lack of hardening and disease interplay with low temperature to cause injury.

Table 7. Effect of summertime irrigation on yield of grasses in fall 1990 and after severe winter conditions in spring 1991 at PARC (Agassiz).
Dry Matter Yeild

(t/ha)*
 
October 1990
May 1991
Grass Prev.

Non-Irrig.

Prev.

Irrig.

Prev.

Non-Irrig.

Prev.

Irrig.

Orchardgrass
Hallmark 2.1 3.1 3.1 0.66
Mobite 1.1 2.2 1.1 0.17
Prairial 2.2 2.9 0.8 0.14
Other Grass
Timothy (Toro) 1.8 2.3 3.7 3.4
Tall Fescue (Johnstone) 2.0 3.4 2.2 1.5
Meadow brome (Regar) 1.6 1.9 2.9 2.6
Reed canarygrass (Palaton) 1.3 1.7 2.2 2.4
*For T/ac divide by 0.45

In the winter of 1990-91, a combination of circumstances contributed to the devastating losses. Rainfall in November was nearly three times average and temperature was above normal. Both factors delayed cold hardening. In December, temperatures fell sharply on two occasions with little snow cover at the time:

- Dec. 17 / 11°C (52°F)
- Dec. 18 / 3°C (37°F)
- Dec. 19 / -12°C (10°F)
- Dec. 27 / 7.5°C (46°F)
- Dec. 28 / -14.5°C (6°F)

In early January, crops were subjected to severe desiccation for nine successive days when conditions were clear, cold and windy.

These winter conditions decimated stands of perennial ryegrass, Italian ryegrass, winter wheat and white clover. Timothy, fall rye and tall fescue generally survived with little injury. Survival of orchardgrass was more variable. Fall application of nitrogen increased damage and late-maturing varieties were generally less hardy than early-maturing ones.

  Date Of First Havest

% cover
Early May Mid May
Pure stand    
Hallmark (early) 100 100
Mobite (late) 100 100
Mixed stand    
Hallmark (early) 72 81
Mobite (late) 28 19

A study at PARC (Agassiz) showed that irrigating orchardgrass in July and August of 1990 increased winter injury and decreased spring growth in 1991 (See Table 7). In fact, irrigated orchardgrass varieties generally did not recover from the winter damage whereas un-ir-ri-gated varieties did. This finding was very surprising given the long and wet interval between the irrigation events and winter and suggests that preconditioning of plants to winter occurs earlier than might be expected. Irrigation had only a slight effect on tall fescue and no effect on timothy, meadow bromegrass and reed canarygrass, all noted for being very winter-hardy.

Competition

Fig 4. Sumas Prairie under water in November, 1990. High water table and flooding are especially damaging to orchardgrass.

As discussed above, competition occurs among plants of the same species so that the stronger plants occupy increasingly more space at the expense of weaker plants in a process referred to as self-thinning. According to Darwin, competition among similar individuals of the same species is more intense than among individuals of different species. Indeed, new species with different ecological niches evolve to reduce direct competition. Normally, competition among individuals of a single species goes unnoticed. A study was conducted at PARC (Agassiz) to evaluate the effects of competition between an early and late cultivar of orchardgrass (see Table 8). The cultivars were seeded alternately in double rows spaced 10 cm (4 in) apart so that they could easily be distinguished. The varieties could also be identified by colour differences.

Three years after planting, the pure stands of both varieties were complete. However, in the mixed stand, the early-maturing variety prevailed over the late-maturing one probably due to early season shading. This effect was more pronounced with late than with early harvest.

This study revealed aggressive competition among varieties of the same species. Evidently, it is easier to maintain grass populations in pure stands than in mixtures. Interestingly, although the variety Mobite declined dramatically in the mixed stand, dead plants were rarely seen.

Disease - Cocksfoot Mottle Virus (CMV)

Cocksfoot mottle virus (CMV) infects orchardgrass and is well known in many regions around the world that produce orchardgrass. In Japan, CMV is considered the most serious disease of orchard-grass. PARC scientists first positively identified this virus on farm fields in BC about eight years ago. CMV is probably widespread in both coastal BC and the Pacific Northwest.

The disease is most easily noticed in late March or early April when plants are less than 30 cm (12 in) tall. Distinctly yellowish (sometimes mottled) plants are scattered around fields (see Fig. 5). The disease is most prevalent in older stands because it builds up gradually. The pathogen does not survive in the soil and is not carried by seed so most new stands are disease-free. The disease is spread from infected plants by certain beetles but more commonly by harvesting equipment. The disease is less common on pastures than mechanically-harvested fields.

Plants infected with CMV lose vigour and eventually die. Because infected plants diminish and die, it is rare to see more than 10% infected plants in a field. CMV is very likely a major cause of stand decline and weed encroachment in orchardgrass in our region. There is no information on whether CMV reduces forage quality.

To reduce spread of the disease, farmers should plant resistant varieties (consult extension agent). Cleaning harvesting equipment, especially after harvesting older infected fields will slow spread of the disease. Harvesting clean fields before infected ones should also help to slow the spread of CMV.

Insects - Leatherjackets

Leatherjackets are serious pests of forage crops and lawns in many parts of coastal BC and the Pacific Northwest. The first North American report of leatherjackets came from Cape Breton Island, Nova Scotia, in 1955 and the first BC sighting was in lawns in Vancouver in 1965.

Leatherjackets are the larvae of the European marsh crane fly, which resembles a giant mosquito with a body length of 2.5 cm (1 in - Fig. 6). The crane fly has one generation per year. Adults emerge from the soil in August and September and mate immediately. Each female lays about 280 shiny black eggs in the grass within 24 hours of emerging. Adult crane flies live only one week.

The eggs hatch within two weeks into grey, legless 3-mm (1/8-in) long larvae with a tough leather-like skin, giving its name. The larvae (leatherjackets) feed on the crowns and tops of grasses in the fall and over-winter in the larval stage. The larvae can withstand both cold weather and flooding. The leatherjackets resume feeding in spring as the soil warms, causing most damage in March and April. They do little feeding after they reach full size in May. Heavily infested grass stands produce little growth before mid-May. Leatherjackets pupate in July and August and the mature pupae work their way to the surface to protrude about 1 cm (1/2 in) when the adults emerge.

Leatherjackets are too small to be easily detected in the fall. The best time to test for leatherjackets is after they begin to actively feed in early March. At least ten different locations in a field should be tested, including high and low areas. The simplest method is to force the leather-jackets to the surface by applying gasoline at a rate of 250 ml (one cup) per 30x30 cm (1 sq. ft.) of area. A more accurate method is to dig up 15 x 15 cm (6 x 6 in) pieces of sod about 5 cm (2 in) deep and submerge in a pail containing a saturated salt solution (saturated salt solutions will float a potato). Wait for 5 minutes and the leatherjackets will float to the surface where they can be counted.

Typically, control is warranted when more than 20 leatherjackets are seen per 30 x 30 cm (1 sq. ft.) area. Consult local pesticide recommendations for the latest approved control method.

Mammals - Moles

Moles are small greyish-black tunnelling mammals that have tiny or no eyes. Moles feed mainly on earthworms and both harmful and beneficial soil insects and their larvae. The grass growing above tunnels is usually stunted or killed but the effect on entire fields is usually small. The greatest problem for farmers are the mounds of soil that dull cutting blades and contaminate feeds.

There are no registered methods for baiting or chemically controlling moles in BC. The only available method of control is trapping, typically with English scissor-type traps. Trapping is most effective in November to March. Test for current runways by stamping existing mounds.

Soil Aeration Reduces Compaction In UK Pastures

Soil compaction is inevitable in high rainfall areas on farms with relatively fine-textured soils. These are soils with a high clay or silt content. Grazing by dairy cows on wet soils causes hoof imprints (called poaching) which reduce water movement through the soil. Tire tracks caused by heavy equipment have a similar effect.

Scientists at the Department of Agriculture of University College of Wales have studied the effect of slitting compacted soil with a soil aerator. The soils studied had a compacted layer at about 10-12 cm (4-5 in). The aerator had 15-cm (6 in) long tines. The fields were 20-year old pastures of perennial ryegrass.

Table 9. Effect of slitting (aerating) compacted silty loam on yield and nutrient uptake by a perennial ryegrass sward in the U.K.

Control Aerated
kg/ha (lb/ac)
Daily Growth 25 (22) 54 (49)
Daily N Uptake 1.3 (1.2) 2.6 (2.3)

The scientists found that penetrating the compacted layer of soil with the aerator could double forage production and nutrient uptake. They concluded that the field used in their study was more compacted than average but that the effect was so great that even fields with less compaction would benefit.

Ploughing also reduces compaction, but ploughing is expensive, takes land out of production for a period and tends to bring up stones. And the benefits of ploughing may be quite short term. Research is being conducted at PARC (Agassiz) to use soil aeration to improve manure absorption into grass fields and to reduce runoff from sloped land.

Chapter 7: Forage Quality

Plant Structure

The defining characteristic of forages is that they contain a large portion of cell-wall material. The amount and type of plant cell-wall material determines the nutritional quality of forages.

A young plant cell has a single outer layer referred to as the primary cell wall (Fig.1). As the plant matures, a second cell wall is laid down on the inside of the cell. The secondary wall is thicker than the primary wall, giving cells tensile strength. The primary and secondary cell walls combined make up 40-80% of the forage dry matter. The main structural components of both primary and secondary walls are two complex carbohydrates called cellulose and hemicellulose. Cellulose is one of the most abundant organic materials on earth. Because higher animals cannot produce enzymes that digest cellulose, they make use of cultures of microorganisms residing in their digestive tracts. Ruminants have the most efficient system for digesting and utilizing cellulose.

 
Fig 1. Diagram of a plant cell showing cell-wall structure.

With advancing maturity, forage cells insert a non-carbohydrate material known as lignin into the primary and secondary walls. This complex compound is the main constituent of wood and gives the plants additional tensile strength and rigidity. Lignin can be thought of as the primary skeleton of the plant cell. Lignin is important from a nutritional perspective because it is totally indigestible and its presence reduces the availability of the cellulose and hemicellulose portions of the forage. The primary cell wall is like a layer of bricks, the secondary wall like a layer of cinder blocks laid inside the bricks and lignin is like mortar added later between the bricks and cinder blocks. As the plant advances in maturity, more lignin is added to the complex of brick and blocks making them more difficult to break down and digest.

Microwave method to determine moisture content of forage

Supplies: Microwave oven; small scale capable of weighing up to 150 grams (10 oz.) in small increments (2-5 grams; 0.1 oz. or smaller); dry, dinner-size paper plate; glass of water.

Method: Select a representative sample of forage from all over the field. Samples should be taken from top, bottom and middle of swath. Weigh the empty paper plate and record the weight on the edge of the plate.

Weigh exactly 100 grams of forage onto the plate on the scale, allowing for the weight of the plate. (For example, if the plate weighs 30 grams, the total weight of the plate and forage is 130 grams.) For US measurements use exactly 10 oz. of sample plus weight of plate.

Spread the sample evenly over the plate and place it in the microwave with a half-filled glass of water in the back corner. Heat the sample for four minutes at full power.

Weigh and record the weight, then stir the forage and place the plate back in the microwave for another minute, taking care not to lose any of the sample.

Heat at full power but for only 30 seconds before weighing. Repeat the procedure until weight becomes constant. If the forage starts to char, shorten the drying intervals.

The final constant weight, minus the weight of the plate, is the dry matter content of the forage as a percentage. (For US measurements, multiply the final weight, minus plate, by 10 to get percentage dry matter.)

 

 

Assessing Forage Quality

Taking the sample

Accurate results are dependent on obtaining a representative sample, proper handling of the samples after collection and good analytical procedures in the laboratory.

Sensory appraisal

Forages can be evaluated by sight, smell and feel. Useful sensory clues include: colour, leaf content, stem texture, maturity, contamination by weeds, mold or soil and observations on palatability.

Dry matter determination

Dry matter is the percentage of the forage that is not water. Dry matter content must be known to compare yield of different forages and dry matter content affects feed intake. Dry matter content also determines how forages will preserve when stored as hay and silage.

Fig 2. The detergent (Van Soest) procedure to partition forage fractions.

What is 'Detergent' Fibre?

The detergent method for assessing quality of forages was developed in the 1960's. The earlier crude fibre system failed to generate accurate estimates of digestible nutrients over a wide range of forages; it tended to underestimate good quality forages and overestimate poor quality forages. The detergent system of forage analysis is now the most common way to assess forage quality. Fig. 2 shows a schematic of the detergent system of forage analysis. Detergent analyses are performed on dried and finely ground samples.

Table 1. Clasification of forage fractions using the Van Soest method.
Fraction Components Included Digestibility
Cell Contents Sugars, starch, pectin, Complete
Soluble carbohydrates Complete
Protein, Non-protein N High
Lipids (fats) High
Water soluble vitamins minerals  
Cell Wall (NDF) Hemicellulose Partial
Cellulose Partial
Heat damaged protein Indigestible
Lignin Indigestible
Silica Indigestible

Neutral Detergent Fibre (NDF)

For determining NDF, samples are boiled in a special detergent at a neutral pH of 7.0, then filtered. The soluble portion that passes through the filter contains the highly digestible nutrients contained within the cells (see Table 1).

The insoluble portion of the forage that does not pass through the filter is called the neutral detergent fibre. This fraction contains the cell-wall material including cellulose, hemicellulose, lignin and silica (Table 1). NDF fraction increases with the advancing maturity of forages.

Neutral detergent fibre is used as a negative indicator of feed intake. As the NDF increases, animals are able to consume less forage. An approximate relationship between NDF and intake is:

Feed intake (dry matter) as percent of body weight = 120/NDF%

Example: a forage with an NDF value of 40% will be consumed at 120/40=3% of body weight.

Acid Detergent Fibre (ADF)

Acid detergent fibre is the portion of the forage that remains on the filter after the forage sample is treated with a detergent and strong acid. It includes the largely digestible cellulose, indigestible lignin and inorganic silica.

Acid detergent fibre is important because it is negatively correlated with digestibility of forages. As the ADF increases, the forage becomes less digestible. ADF is the most commonly used indicator of forage quality.

Total digestible nutrient (TDN) values are calculated directly from ADF values. Note that the relationship between TDN and ADF is affected by crop type and that different labs use different equations. Typical equations are shown below:

Legumes and grasses: TDN=88.9-(0.79 x ADF%)

Corn silage: TDN=87.84-(0.70 x ADF%)

Relative Feed Value

Relative feed value (RFV) is often reported for alfalfa hay sold in the US. RFV combines estimates of dry matter intake (from NDF) with TDN (from ADF). RFV is a relative measurement to help farmers compare feeds. High-quality alfalfa and corn typically have RFV values greater than 130 and may reach over 160. Grasses rarely have values over 120. Does this mean that grasses are inferior feeds or should RFV be used only within forage class?

Lignin and silica

Lignin is the wood-like, non-carbohydrate component that cannot be digested by ruminants. Further, lignin decreases availability of cellulose, hemicellulose and protein. The lignin fraction can be determined by further treatment of the ADF fraction with a very strong acid. Some grasses accumulate large quantities of silica (or sand). The silica fraction is left as ash after a forage sample is ignited in a special furnace.

 

Forage Protein Explained

Sources of protein: microbial and rumen-bypass

All animals need to consume protein to supply the amino acids that are used to build the proteins in muscle, membranes, enzymes and milk. Ruminant animals are different from non-ruminants in how they obtain amino acids. Non-ruminants derive all their amino acids directly from the protein in their feed. Ruminants derive amino acids from two sources: from the microbes that grow in the rumen and are carried to the intestines and from the protein that passes through the rumen; both protein sources are digested in the intestines (Fig. 3). What happens to protein in the rumen?

Protein molecules are broken down by microbes in the rumen into both amino acids and non-protein nitrogen compounds such as ammonia. Rumen microbes feed on both types of nitrogen compounds. The microbes obtain their energy needs from the carbohydrates (sugars, starches, hemicellulose and cellulose) in the forage. The microbial cells that pass out of the rumen and that are digested in the intestines provide about half of the amino acids in high-producing dairy cows. Factors that favour growth of microbes in the rumen also favour amino acid supply to the cow.

Rumen microbes grow best when the supply of energy and protein or nitrogen is synchronized. Slowly digested carbohydrates such as cellulose are most compatible with protein sources having slow rates of degradation that provide a steady supply of nitrogen. Frequent meals also help to provide a steady supply of nitrogen for the microbes.

Highly digestible, immature forages supply the most rapidly digestible carbohydrates and the most readily available energy for microbial growth. With rapid digestion, feed spends less time in the rumen, freeing space for more feed intake. Rapid passage of feed through the rumen also moves more rumen microbes into the intestines.

 
Fig 3. Schematic representation of protein digestion and utilization in the cow.

 
Fig 4. Disappearance of protein fractions in forages as a function of time.

How do forages influence protein supply to ruminants?

Forages make up as much as half of the feed rations of lactating cows and therefore play an important role in supplying amino acids. Coincidentally, forages stimulate chewing and rumination, which promotes the production of up to 150 litres (40 gal.) of saliva a day. Saliva buffers the rumen environment for the microbes.

The proteins in forages contain both degradable and undegradable fractions (Fig. 4). The overall degradability of protein is determined by two factors: portion of protein that is digested in the rumen and the speed of digestion in the rumen relative to rate of passage out of the rumen. The degradable fraction can be subdivided into a rapidly degradable soluble fraction and a slowly degradable insoluble fraction.

A study conducted at the University of British Columbia compared the protein attributes of typical feeds used on dairy farms in coastal BC (Table 2). Surprisingly wide differences in protein degradation were found in each forage type. For example, the slowly degradable fractions in alfalfa hays (from Central Washington) ranged from 17 to 45% (average 33%) and in grass hays ranged from 25 to 63% (average 46%). The slowly degradable fraction in alfalfa was generally digested faster than that in local grass hays. These results show that at present we cannot predict the exact protein characteristics in local forages in order to formulate precise rations.

Table 2. Ratio of rapidly to slowly degradable fractions in forage classes used in coastal B.C.
Alfalfa Hay 2:1
Grass Hay 1:1
Grass Silage 1:1
Corn Silage 3:1
(Adapted from Von Keyserlingk, 1994. Ph.D. Thesis, Univ. of BC.)

Factors which affect the rate of protein breakdown in forages

Feeds pass very rapidly through the rumen of high-producing dairy cows consuming large amounts of feed. Hence, rumen microbes have little time to digest the protein that they require for their own growth. It is important to understand the factors that affect the rate of breakdown of protein in the rumen.

Growing conditions, level of nitrogen fertilization, maturity, time of year and conservation method influence the rumen degradability of forage protein. High rates of nitrogen fertilization decrease the undegradable fraction, hence increase degradability. Increasing stage of maturity and progression of the growing season decrease protein degradability. During the ensiling and drying processes, protein can be damaged by heat, decreasing the soluble fraction and increasing the undegradable fraction.

Grass hay often contains more soluble protein than fresh forage because some insoluble protein is converted to a soluble form during drying. However, hay has a lower protein degradation rate and a larger undegradable fraction than fresh forage, which ultimately results in overall less effective degradation.

During ensiling, enzymes released from collapsing plant cells digest protein into peptides and amino acids. Bacteria further digest the peptides and amino acids into simpler molecules such as amines and ammonia. At the same time, the bacteria consume the sugars in the forages and release acids that have low energy value for rumen microbes. Therefore, ensiled grass usually has a poor balance between available energy and nitrogen for rumen microbes. The changes to protein during ensiling reduce the value of silage protein so that protein supplements must be provided.

When forages are wilted prior to ensiling, the water loss concentrates the salts in the cell solution, which tends to reduce the fermentation of the protein in the silage. Protein breakdown in silage can also be reduced by additives such as formic acid, formaldehyde and microbial inoculants. Formic acid quickly reduces pH and stabilizes the silage, but has no influence on the protein degradation in the rumen. Formaldehyde has a dual action; it kills destructive anaerobic bacteria called 'Clostridia' and decreases protein degradation in the silage and in the rumen by bonding to the proteins.

The Faculty of Agricultural Sciences at UBC has been investigating novel methods for reducing breakdown of protein during ensiling. The research has revealed that protein degradation during ensiling can be reduced by applying so called 'masking agents' that reduce the activity of the protein-destroying enzymes.

Reduction of the degradation of protein in the rumen is beneficial only if the protein escaping degradation in the rumen is digested in the intestines. Forage proteins associated with cell walls escape digestion in the rumen but cannot be digested in the small intestine, and are only slightly digested in the large intestine.

Recent work at the University of British Columbia showed that only 20% of the protein produced by a grass crop stored as silage is absorbed in the small intestines; intestinal absorption of ensiled corn protein is only 10%.

Because so much of the forage protein is digested in the rumen, the composition of amino acids entering the small intestines differs greatly from the composition of the consumed forage. There are also wide differences among forages in how easily amino acids can be absorbed in the intestines, but there are no clear differences among fresh, dried and ensiled forages. The exact requirements of amino acids are still not known. Interestingly, when dairy cows are given diets containing a high proportion of grass silage, the source of supplemental protein has a great influence on milk production.

Conclusion

Current thought is that ruminants have specific requirements for amino acids rather than for certain proteins. However, evaluating protein sources and formulating rations still requires characterization of proteins in terms of their degradability in the rumen. The ultimate goal of new feed models is to formulate rations that meet the precise nitrogen needs of rumen microbes as well as the specific amino acid requirements for each class of ruminant animal.

Contributed by J. Baah and J. A. Shelford, Faculty of Agricultural Sciences, University of British Columbia

Making Silage: The Fermentation Process

Harvesting forages as silage is a compromise between minimizing field and fermentation losses. Efficient fermentation ensures a more palatable and digestible feed, encouraging optimal dry matter intake that translates into improved animal performance. The primary management factors that are under the control of the producer are:

1. Stage of maturity of the forage at harvest.

2. Type of fermentation that occurs in the silo or bunker.

3. Method of harvesting, type of storage structure, silo management and method of feeding.

Attention to details such as speed of harvesting, moisture content, length of chop, silage distribution and compaction can improve the fermentation process and reduce storage losses.

Six Phases of the Ensiling Process

PHASE 1 Aerobic microorganisms are present on the forage surface at the time of harvesting. Aerobic respiration by freshly cut plant material and aerobic bacteria begins at harvesting and continues after the forage is piled and packed. Aerobic respiration consumes the oxygen contained within and between the forage particles creating the desired anaerobic conditions. Aerobic respiration also consumes the soluble carbohydrates needed by the beneficial lactic acid bacteria and by rumen microbes.

Phase 1 ends when all the oxygen has been consumed. Under ideal conditions, Phase 1 lasts only a few hours; with improper management, this phase may continue for several weeks and result in significant reduction in feed quality.

The respiration process produces water and heat in the silage mass. Excessive heat build-up during Phase 1 can greatly reduce the digestibility of proteins. Plant enzymes break down proteins during Phase 1. Proteins are first reduced to amino acids and then to amines and finally to ammonia. Up to half of all the plant protein may be broken down during this process. As the silage becomes more acidic, the activity of these enzymes declines.

Good silage-making technique minimizes air infiltration to shorten the time required to achieve an anaerobic environment. Key management factors are crop choice, content of soluble carbohydrate, crop maturity, moisture content, chop length, rate of filling and packing, and proper sealing of the storage structure.

Table 3. Average nutrient composition of farm-grown forages from the South-Coastal Forage Competition in BC in the years 1993-97. (Courtesy of D. Bates, BC Ministry of Agriculture and Food.)
Nutrient Grass Hay Grass Silage
Low Avg High Low Avg High
Dry matter (%) 80.6 88.1 91.8 19.5 40.2 75.1
Acid Detergent Fiber (%) 23.8 29.8 38.1 23.4 31.2 41.7
Neutral Detergent Fibre (%) 43.9 56.3 65.9 33.3 48.9 65.3
Total Digestible Nutrients (%) 55.8 66.8 74.6 50.8 65.0 75.4
Crude Protein (%) 9.1 17.6 24.4 8.8 17.7 26.1
Nitrogen (%) 1.5 2.8 3.9 1.4 2.8 4.2
Nitrate-N (%) 0.01 0.11 0.40 0.0 0.05 0.26
Ammonium-N as % of total N 3.6 17.5 47.5
Heat Damaged Protein (%) 2.4 4.4 11.2
pH 3.9 4.9 6.4
Phosphorus (%) 0.19 0.33 0.48 0.22 0.37 0.55
Potassium (%) 1.17 3.13 4.99 1.30 3.05 4.50
Magnesium (%) 0.13 0.23 0.38 0.11 0.24 0.53
Calcium (%) 0.26 0.47 0.85 0.28 0.56 1.39

PHASE 2 Phase 2 begins when anaerobic bacteria take over. These bacteria ferment soluble carbohydrates into acetic acid. Acetic acid production is desirable because it reduces pH to set up the succeeding fermentation phases. Also, acetic acid can be used as an energy source by rumen microbes. Phase 2 usually lasts no longer then 24 - 72 hours, ending when the pH of the ensiled mass falls below 5.0, killing the acetic acid-producing bacteria.

PHASE 3 This is a transition phase in which the lower pH favours the growth of an anaerobic group of bacteria that produce lactic acid, replacing those that produce acetic acid.

PHASE 4 In this Phase the lactic acid bacteria predominate. Lactic acid is the most desirable of the fermentation acids. In well-preserved silage, lactic acid should comprise more than 60% of the total silage organic acids and the silage should contain up to 6% lactic acid on a dry matter basis. Lactic acid can be utilized by cattle as an energy source. Phase 4 is the longest phase in the ensiling process as it continues until the pH of the forage is low enough to inhibit the growth of all bacteria. When this pH is reached, the forage is in a stable state so long as oxygen is excluded.

Table 4. Effect of adding absorbent feedstuffs to direct-cut grass silage on effluent and content of water-soluble carbohydrates and crude protein, relative to wilted silage.
Additives Effluent Water soluble carbohydrates Crude protein
% % %
Wilted silage (28% dry matter) 4.5 13.9 22.1
Direct cut silage (16% dry matter) 18.0 12.8 22.5
+ 10% Barley 11.8 16.8 20.7
+ 10% Beet pulp 9.2 23.0 20.5
+ 10% Alfalfa cubes 6.3 12.2 22.3
+ 20% Alfalfa cubes 1.9 14.9 21.3
+ 30% Alfalfa cubes 0.6 16.0 22.3
(based on S. Fransen and F. Strubi. 1998. J. Dairy Sci. 81: 2633-2644)

PHASE 5 The final pH of the ensiled forage depends largely on the type of forage being ensiled and the condition, especially moisture content, at the time of ensiling. Haylage should reach a final pH of around 4.5 and corn silage near 4.0. Drier silage generally has higher stable pH than wet silage. The pH alone is not a good indicator of the quality of silage or of the type of fermentation that occurred.

Forages ensiled at moisture levels greater than 70% may undergo a different version of Phase 4 where undesirable Clostridia bacteria proliferate instead of lactic acid bacteria. Clostridia bacteria produce butyric acid rather that lactic acid, which results in sour silage. With this type of fermentation the pH may stabilize at 5.0 or above.

PHASE 6 This phase refers to the silage as it is being fed out from the storage structure. This phase is important because up to 50% of the silage dry matter losses occur from secondary aerobic decomposition. Phase 6 occurs on any surface of the silage that is exposed to oxygen while in storage and in the feed-bunk. High populations of yeast and mould can lead to significant losses due to aerobic deterioration of the silage. Proper management is vital to reduce these losses and improve the bunk-life (aerobic stability) of the silage.

Absorbents Reduce Silage Effluent

Silage effluent represents a loss of valuable forage nutrients. Effluent is also a potent environmental pollutant that poses a threat to fish habitat because of its very high biological oxygen demand (BOD) and high concentrations of soluble protein and ammonia. The best way to minimize effluent from silage is to wilt the crop prior to harvesting, but poor weather when the crop is ready for harvest may make wilting impossible. Under these conditions, absorbents may be added to silage to reduce effluent.

A study conducted by Washington State University at Puyallup compared the effectiveness of different absorbents in reducing effluent from direct-cut silage. There was little effluent when the dry matter content of the silage was above 27%, but below 20% dry matter effluent loss ranged from 10 - 20% of the dry matter (see Table 4). The study showed that adding 10% barley, beet pulp, or alfalfa cubes successfully reduced effluent, but alfalfa cubes were the most effective of the three additives at equivalent weight. In terms of effect on nutritional quality, beet pulp raised the concentration of water-soluble carbohydrates most but alfalfa cubes increased crude protein the most. Cost of additives was not considered in this study.

The Fescue Endophyte Story

Tall fescue rapidly became the most important cultivated forage grass in the US after its introduction in 1931. Farmers quickly recognized that tall fescue is well adapted to a wide range of soil and weather conditions and offers a considerable advantage in yield over many other grasses.

Unfortunately, several health and performance problems were reported in stock feeding on tall fescue. These included low feed intake, low weight gains, poor reproductive performance, lower milk production and higher body temperature. The syndrome had a number of names including fescue toxicosis and summer syndrome. The reasons were not apparent from chemical analysis of the feed.

The first clue to the cause of fescue problems came in 1976 when researchers in the state of Georgia discovered that problem pastures were heavily infected with a fungus living in the fescue plants whereas uninfected pastures were free of animal health problems. The uninfected pastures had been inadvertently established with old seed in which the fungus had died before planting. Numerous trials have since shown that the fungus causes low feed intake, poor animal gains, low conception rates and poor milk production.

The offending fungus is referred to as an endophyte because it lives within the plant without parasitizing or harming it. The fungus cannot be seen with the unaided eye but can easily be detected in a laboratory. Curiously, the fungus offers infected plants some protection against insects, diseases, and even environmental stresses such as drought. While forage seed producers are working to eliminate endophyte from their seed, turf producers are putting endophyte back in to take advantage of this protection. The fescue endophyte fungus goes by the name Acremonium coenophialum.

The endophyte is now known to be transmitted only by seed so it cannot spread across fields or even from plant to plant. A new stand of tall fescue planted with clean seed will not contain any endophyte-infected plants. All certified tall fescue seed is now endophyte-free.

Using Maturity Differences To Spread The Harvesting Season

Spring maturity of grass varieties adapted to coastal BC and the Pacific Northwest ranges by as much as 3 - 4 weeks based on comparable growth stages. Therefore, producers can plant a set of varieties with contrasting maturities so that they will be able to harvest all crops at the appropriate growth stage. Having a range of maturities is also a hedge against a stretch of bad weather.

A study at PARC (Agassiz) compared early- and late-maturing varieties of orchardgrass, tall fescue and perennial ryegrass in terms of yield and nutritional quality.

When harvested on the same day, the late maturing varieties of orchardgrass yielded 10 - 20% less in first cut than early varieties. On the other hand, when the early and late varieties were harvested at the same growth stage, say 'late boot', their annual yield was similar. Although annual yield was similar, seasonal distribution of yield was not. First harvest taken at the boot stage yielded 25% of annual production for the early variety, but over 40% of annual production for the late variety. Note that this means more eggs in one basket for the late variety, which partly offsets the advantage of the hedge against poor weather mentioned above. Research at PARC (Agassiz) has shown that the late varieties require more fertilizer for first cut than early varieties (see Ch. 3).  

Table 5. Yield and quality of early (Hallmark) and late (Mobit) orchardgrass varieties harvested at the 'boot' growth stage. Hallmark matures about three weeks before Mobite.
Early

Maturing

Late

Maturing

Yield t/ha of dry matter *
Annual yield 14.0 13.5
First harvest yield 3.5 5.4
First harvest as % of annual yield 25% 40%
Quality of First Cut %
Crude protein 17.0 11.0
Neutral detergent fibre 58.2 60.9
Acid detergent fibre 30.5 33.5
Lignin 3.1 4.2
*for T/ac multiply by 0.45

As expected, when compared on the same calendar date, the nutritional quality of the late variety was much better than the early variety. Surprisingly, early varieties had better nutritional quality than late varieties when compared at the same growth stage. For example, at the boot stage, the late orchardgrass had 3% more ADF, 2.5% more NDF, 1.1% more lignin, and 3-6% less crude protein than the early variety.

The same trend was observed for perennial ryegrass and tall fescue. Perennial ryegrass has a maturity range of up to four weeks while tall fescue has a range of up to three weeks.

What do these results mean for selecting varieties and scheduling harvests? Indeed, use late-maturing varieties to spread out the harvest season- loss in yield, if any, will be small. You may delay harvesting the late varieties but not as long as indicated by their growth stage. For a late variety that matures two weeks later than an early one, harvest only one week later to ensure comparable quality. Note that late varieties should receive a greater proportion of the annual fertilizer allocation for the first harvest compared to early varieties.

Leaf Diseases Reduce Nutritional Quality Of Grasses

The long growing season, moderate temperatures, high humidity and mild winters support the growth and survival of pathogenic organisms in coastal BC and the Pacific Northwest. The most important leaf disease in the region is stripe rust in orchardgrass. As the name suggests, stripe rust pustules are arranged in characteristic stripes on the leaves. Outbreaks of stripe rust strike south coastal BC in late summer and fall.

Stripe rust overwinters in BC only in the very mild years. More commonly, it blows in from southern Oregon and northern California on southerly summer winds. Once established, the pathogen prefers warm dry days with 2-3 hours of morning dew on the leaves. Under these favourable conditions the stripe rust fungi can double in number every 4-5 days.

Stripe rust reduces digestibility of orchardgrass and increases both acid (ADF) and neutral detergent fibre (NDF) values. There is a direct correlation between visual severity of the disease and increase in ADF concentration (Fig. 5). Effect on protein content is less pronounced.

Fig 6. Variety differences in resistance to stripe rust.

Farmers can minimize the impact of stripe rust by planting resistant varieties of orchardgrass (contact supplier), planting some land to tall fescue, providing ample fertilizer and water and harvesting soon after the disease appears.

Other fungal diseases are thought to have a similar effect on quality although there is less direct evidence. Tall fescue and perennial ryegrass are resistant to stripe rust but both grasses are susceptible to crown rust and stem rust. These diseases tend to proliferate earlier in the season than stripe rust.

Leaf scald overwinters locally and is favoured by cool humid conditions in spring and early summer. The disease starts with scald-like lesions on leaves that spread and kill off large segments turning them brown