Beneath the snow now blanketing Michigan’s corn fields lays a valuable but underused commodity: corn stover. The term “stover” refers to all of the leaf, stalk and cob tissue commonly left after grain harvest. Grain gets all of the attention, but only accounts for 50 percent of each corn crop by weight. This means that the average acre of corn in Michigan yields approximately four tons of stover material on an annual basis. Corn stover has traditionally been returned to the soil as an important source of organic matter and plant nutrients. Yet, increasingly tight margins in the crop and cattle sectors have some producers looking to capture additional value from this abundant co-product.
In some ways, harvest and feeding of corn stover seems perfectly simple. Volatility in hay and corn grain markets, made worse by the drought of 2012, has pushed livestock producers to seek out alternative forages. Due to its relative low cost and ubiquitous availability, corn stover is quickly gaining recognition as a viable option for a portion of the forage component in ruminant livestock rations. Corn stover’s greatest drawback is the fact that it contains only one-third the protein of average quality hay. Yet careful supplementation of stover with high protein feeds like forage brassicas or dry distiller grains can overcome this deficit.
However, it is important to remember that removing crop residue from the field has the potential to negatively impact long-term soil health. Stover protects the soil from the erosive forces of wind and water. It also returns carbon and nutrients to the soil as it is decomposed by soil biota. Fortunately, a tool known as the Lucas Soil Organic Matter Calculator now makes it possible to use baseline soil data and information regarding production practices like tillage, manure and cover crop use to predict how much corn stover could be removed without compromising soil health. Stover harvest activities should generally be concentrated on fields receiving abundant organic matter inputs in other forms.
Grazing is likely the simplest way to capture additional value from corn stover. An average acre of stover will feed a single cow for 30-45 days. Like any grazed forage, feed quality will decline every day animals are on stover and supplemental feeding will be necessary to maximize utilization. Yet extending the fall grazing season can be invaluable in years when forage yields are low and prices are high. Producers commonly face several obstacles to stover grazing including field location, fencing options and access to water. Despite these challenges, grazing is almost always more efficient than stover harvest, transport and manure hauling.
Mechanical stover harvest is facilitated by using a stalk shredding-type combine head during grain harvest and removing the chaff spreader from the rear of the combine. If a stripper head is used, an additional flail shredder or discbine pass will generally be required. Specialized combine attachments have been developed to windrow corn stover, but they are not necessary for a successful harvest. Raking may or may not be recommended based on an individual’s yield goal or the crop’s moisture level. While baling for dry storage can work in ideal circumstances, stover is often too wet to preserve in this manner. Ensiling chopped or baled material is often the best approach and also improves stover’s feed value.
At an average removal rate of two tons per acre, the fertilizer value of corn stover and equipment costs associated with harvest together total about $59 per ton. This is a great improvement over the current market value of $150 per ton for hay. Even with protein supplementation, a stover based ration could save $0.71 per head per day, or $127.61 per cow over a standard 181-day winter feeding period. Despite the potential savings, Michigan State University Extension recommends using ration balancing software when deciding how much stover to feed.
Corn stover has long been an important resource on the farm, but the number of ways it can be used is expanding. In addition to harvest as forage, the recent construction of ligno-cellulosic ethanol biorefineries in the Midwest has created market opportunities for corn farmers to sell stover biomass for processing into liquid fuel. Three ethanol plants in the central Corn Belt are now in the process of contracting with farmers to supply approximately 275,000 tons of corn stover per facility in 2014. These emerging markets provide practical ways for Michigan corn growers to extract additional value from their product and remain competitive.
- Sustainable Crop Removal: Maintaining Soil Quality, MSU Extension Bulletin E-3079
- Sustainable Corn Stover Harvest, Iowa Corn Promotion Board
- Corn Stover Harvesting, Cattle Call Vol 12, Iss 2