Corn is one of the great world crops. A unique, warm-season, New World cereal-grass, corn is grown on millions of hectares around the world to feed mainly monogastric and ruminant livestock. This is grain corn. Corn for silage is largely a forgotten cousin in the corn world. Compared to grain corn, it is smaller in acreage, full of water, inherently unstable and variable and almost impossible to sell or transport.
But for ruminant producers, and most notably for dairy producers, silage corn is a crop like no other. Testimony to this are the near-heroic efforts to extend the range and uses of silage corn, breeding ever more rapidly maturing hybrids with vigorous cool-weather growth and even planting the crop under plastic in cool regions such as Ireland and Newfoundland.
There are also serious ventures to use whole corn plants as winter pasture (see Section 7)! What makes corn unique as a silage crop? High energy content, high digestibility, ease of ensiling, relatively stable and consistent quality, and of course, superior yields. No other crop offers all these advantages. Cattle farmers have long known the virtues of silage corn. But silage corn as a distinct crop has emerged only in the past decade or so when plant breeders started to identify genotypes with, not only good agronomic traits and grain yields, but also attributes of special importance for whole-plant silage use. These attributes include leafiness, stay-green leaves, stovers with low fibre concentration and high fibre digestibility, soft starch, and high whole-plant yield. In Section 1, a corn breeder describes how new corn hybrids are bred while several seed companies reveal their strategies for breeding silage-corn.
The quality of silage corn has improved, not only through breeding, but thanks also to a better understanding of crop maturation (Section 6), to new harvesting techniques such as silage processing, and to storage enhancement tools such as silage additives (Section 7). As the quality has improved, farmers have been increasing the proportion of corn silage in cattle rations. The nutritional attributes of corn (fibre and fibre digestibility, protein and fats) are also described in Section 7, as are potential problems with feed rations that are high in corn silage and health risks from mycotoxins. Some large cattle operations now contract production of silage corn or purchase the crop from speciality growers; in Section 7 you will find a method of valuing the silage corn crop based on its nutritional quality.
With silage corn emerging as a major crop in its own right, concerns have grown over the possible impact on the environment of growing this crop. Growing any corn presents some environmental risks, due to long periods with little or no soil cover after harvest, tillage practices that can lead to erosion, and the use of chemicals to control pests. Added to this are special concerns of producing silage corn, namely the absence of crop residue on the soil after harvest and, oftentimes, the use of high nutrient inputs in the form of animal wastes. Paradoxically, in a whole-farm context, silage corn can improve nutrient conservation by reducing the need for importing feed by improving the balance of nutrients produced on the farm (Section 2).
The many challenges of managing nutrients on silage corn fields are discussed in Section 2. For example, there are the benefits of injecting and incorporating manure to reduce ammonia loss to weigh against risks to water quality associated with below-ground slurry application. Providing enough P during early growth is a special challenge for corn growers, who must also understand the complex chemistry of P in manure so that they can comply with standards for protection of water quality, such as the Phosphorus Index. To manage nutrients effectively and safely, it is helpful to understand the role of each nutrient in the growing crop, the complexity of soil testing, and the practical side of manure testing. Matching corn with suitable winter cover crops can help to guard against nutrient runoff and soil erosion (Section 4).
Some of the information in this book was borrowed from studies on grain corn, because of a dearth of studies on silage corn. For example, the sections on tillage practices and soil compaction (Section 3) are based largely on studies on grain corn production, which is somewhat unfortunate because of the large difference in amount of crop residue for the two crops. Most of the information on pests (diseases, nematodes and weeds) was developed for grain corn but applies well to silage corn (Section 5).
‘Advanced Silage Corn Management’ might well have been titled ‘Perspectives in Silage Corn Production’. We did not write a primer for the beginner. We have not attempted to cover all topics, target all regions, nor to answer all questions. Rather, we have assembled the insights of a wide range of experts, working in diverse corn growing regions, on subjects of special importance to silage corn producers. Our goal was to stimulate silage corn enthusiasts with a unique collection of information.
C. Grant Kowalenko