Project Interim Report: Optimizing corn–cover crop systems for production of dairy feed in a changing climate in B.C., Canada (March 2017)

Interim Report March 2017


Aerial view of complexity of agriculture in the south-coastal region of British Columbia with high winter rain and moderate air temperatures

Overall Objectives
The overall objectives of a series of Pacific Field Corn Association Projects can be summarized as follows.

  1.  To increase the adaptive capacity of producers by helping them balance the use and management of the summer and winter season crops through species / variety selection and planting / harvesting dates. This approach will enable farmers to adapt to changes in overall weather as well as seasonal weather (e.g. milder, wetter winters / warmer and drier summers).
  2. To increase adaptive capacity of producers by providing tools to optimally balance land allocation of perennial and annual crops so as to maximize and stabilize production of essential farm nutrients (crude protein, neutral detergent fiber, digestibility etc.).
  3. The adaptive capacity of farmers will be helped by reducing dependence on imported feeds and reduced burden of excess nutrients.

Specific Objectives
The specific objectives of this corn-cover crop study were to:

  1. optimize year-round production of corn and winter cover crops to help dairy farms in south-coastal BC reduce dependency on feed imports.
  2. find the ideal combination of corn maturity, corn planting date, corn harvest date, and cover crop species to maximize year round production of quality dairy feed.

Modern dairy operations often depend on significant amounts of purchased feed to meet nutritional needs of high producing cows. These feed imports add economic and often environmental burdens, especially if land is limited.

In south-coastal BC, dairy production is intensive due to expensive land. About 60% of feed is grown on the farm and consists primarily of grass hay and grass and corn silage production. About 40% of feedstuffs are imported which includes mostly concentrates such as distillers grains, rolled barley canola meal and soybean meal. Some purchases may include straw for supplemental fiber and alfalfa.  On-farm corn yield can range from 15 to 25 tonnes of dry matter/ha/year providing highly digestible, high energy silage. Grass production is mostly from orchardgrass and tall fescue with some perennial ryegrass crops. The grasses are usually preserved as hay, haylage or silage providing fiber, energy and protein for the cow’s diet. Grass is often cut 4 to 6 times annually with yields ranging from 8 to 16 tonne DM/ha/year.


Figure 1. Simplified overview of typical dairy feeds.


The study is designed to examine all combinations of 2 planting dates x 2 harvesting dates x 2 corn maturities matched with 4 winter cover crops grown in the periods between corn harvest and corn planting. The study was conducted on a well to moderately drained silt loam soil. The two silage corn hybrids were Pioneer P7443R (early maturity, 2100 CHU Canada, 70 day USA) and Hyland HL SR35 (late maturity, 2700 CHU Canada, 88 day USA). The four cover crops were:

  • Farm standard = Winter wheat
  • Legume = Common winter vetch
  • Highest yield = Fall rye
  • Highest feed quality = Italian ryegrass

      Total fertilizer nitrogen application for the entire year was 300 kg N /ha (270 lb/ac) applied as ammonium nitrate (no manure or manure history in this trial). This was split as 1/3 applied late winter/early spring to the winter cover crops and 2/3 applied pre-plant to the corn crop. Other nutrients (phosphorus, potassium, sulphur, magnesium, micro-nutrients) and Calpril lime were applied according to soil test recommendations. The study was started in spring of 2015 and this report covers all the data to date: two production years (2015 and 2016) for corn silage and one for winter cover crops (2015-2016). Statistically, the design of the study is a split-split plot, with the main plot being harvest/planting date, the sub-plot as corn hybrid and the sub-subplot as winter annual crop. Each individual study treatment was repeated four times. In all, there were 32 combinations: 2 planting dates (early and late) x 2 harvest dates (early and late)  x 2 corn hybrids (low and high heat unit) x 4 winter annuals (fall rye, winter wheat, Italian ryegrass and winter vetch).


 farm calendar

Figure 2.  Study Farm Calendar – showing one corn hybrid with four winter cover crops and 16 combinations.


Figure 3

Figure 3.  Corn plots 2015 showing early corn growth from two planting dates.


Figure 4

Figure 4.  Corn plots 2016 showing mid-season corn growth from two planting dates.


Figure 5

Figure 5.  Corn/Annual plots 2016 showing early corn growth and late harvested winter annuals.


Figure 6

Figure 6.  Corn plots 2015 showing late harvested corn plots and early planted winter annuals.



Results from the first two season of corn production and the first winter of cover crops are presented in Tables 1 to 4.

For corn silage production there was no significant effect on corn silage yield from previous winter annual for 2016. Highest corn yield was obtained for the ‘Early’ planting / ‘Late’ harvest system for both the low and high CHU hybrids in 2016 and the high CHU in 2015. See Table 1.

Table 1. Corn Silage yield (t DM ha-1) 

Plant Harvest Early Maturing Corn (Low CHU)Late Maturing Corn (High CHU)Early Maturing Corn (Low CHU)Late Maturing Corn (High CHU)
EarlyEarly9.5b 10.7ab 14.8b  15.0b
EarlyLate9.7b 12.4a 16.1a 16.9a 
LateEarly9.5b 10.3ab 12.1d 11.7d 
LateLate10.7ab 12.0ab 14.2c 13.6c 

      * means with all different letters are significantly different within a year (P<0.05).  This table shows that highest corn yields with early corn planting and late corn harvest especially with a late maturing corn hybrid. For late planting and early harvest, which is sometimes a necessity, early hybrids have lower yield but much better grain content and better cover crop yields (see tables below). Early corn plus cover crop is a climate-smart strategy. Late corn with cover crop will be best in a great year but carries more risk.


The early maturity corn hybrid (Low CHU) had significantly higher grain percentage than the late maturing hybrid (High CHU) in both 2015 and 2016. Highest grain percentage was obtained for the ‘Early’ planting / ‘Late’ harvest system for both the low and high CHU hybrids in 2016 and the high CHU in 2015. See Table 2.  Poor grain contents are highlighted.

Table 2. Grain percent

PlantHarvestEarly Matuing Corn (Low CHU)Late Maturing Corn (High CHU)Early Maturing Corn (Low CHU)Later Maturing Corn (High CHU)
EarlyEarly60.1a41.5d38.9c 18.3e

       *means with different letters are significantly different within a year (P<0.05)

There was no significant effect on winter annual yield from previous corn hybrid. Highest yields were obtained from Late planting/Early harvest of corn which equals Early planting/Late harvest of winter annual. Highest yields were obtained from Fall Rye and Winter Wheat. See Table 3.

Table 3. Yield of winter cover crop as affected by corn management, in spring yield 2016 (t DM ha-1)

Corn Dates Planting-Harvestingdays plant to harvestFall RyeItalian RyegrassWinter VetchWinter Wheat
Low heat unit corn     
Early - Low - Early2284.
Early - Low - Late 210 3.3 2.4 1.3 3.1 
Late - Low - Early 242 6.6 5.4 2.6 7.8 
Late - Low - Late 224 5.8 4.7 2.5 6.2 
High heat unit corn     
Early - High - Early 228 4.1 3.3 1.5 4.5 
Early - High - Late 210 3.5 2.1 1.3 2.9 
Late - High - Early 242 6.5 5.7 2.5 7.2 
Late - High - Late 224 5.8 4.5 2.1 6.0 

Table 3 shows highest cover crop yields with late corn planting and early harvesting because this gives the cover crop the most time to grow. Second best and almost as good is late planting and late harvesting of corn. This shows the importance of allowing time for cover crops to grow in spring when days are longer and growth rate is faster than in fall.  

Highest overall yields over 18 months were obtained with “Plant Early” Late Maturity-High CHU and “Harvest Late” combined with Fall Rye or Winter Wheat. Significantly higher Grain % was obtained with “Plant Early” Early Maturity-Low CHU and “Harvest Late” combined with Fall Rye or Winter Wheat which has significant implications for feed energy value and digestibility. See Table 4.

Table 4. Corn and cover crop yields and 18-month totals for low corn heat unit corn harvested early and high heat unit corn harvested late (t DM ha-1).  All corn was planted early.

 Low CHU corn Harvested EarlyHigh CHU corn Harvested Late
Corn Yield 20159.512.4
Corn Yield 201614.816.9
Winter Wheat4.53.1
Fall Rye4.23.5
Italian Ryegrass3.32.4
Grain % 201560.153.2
Grain % 201651.827.7
Total Yield (2015-2016)  
Corn + Winter Wheat28.832.5
Corn + Fall Rye28.632.9
Corn + Italian Ryegrass27.731.8

This table shows that late harvest of high heat unit corn yields more than early harvest of low heat unit corn but cover crop yield reduces the difference and provides a measure of insurance against poor summer weather. 


figure 7

Figure 7. Total yield of corn (2015, light blue and 2016, dark blue) and cover crop (2015-2016, winter wheat, light green; winter vetch, yellow; Italian ryegrass, dark green; Fall rye, purple) of all 32 cropping combinations. Description on the left indicates: corn planting date (Early or Late) followed by Corn heat unit rating (Lo or Hi) followed by corn harvest date (Early or Late). Total yields ranged from about 21 to 33 t/ha over this period.


 ‘Early’ planting / ‘Late’ harvest system produces highest yields for corn. ‘Late’ planting/ ‘Early’ harvest system produces highest yields for winter annuals. Combinations of corn maturity, planting date, harvest date, and cover crop species significantly change total yields of year round feed produced for dairy operations. Different management combinations produce significant differences in corn silage grain percentage and maturity stages of winter annuals which are expected to affect quality of feed produced.