By Tony Bailey
Chopping corn for silage is tough on soils. The Indiana Agricultural Statistics Service estimates that 100,000 acres of silage were harvested from Indiana soils in 2018.
Silage harvest leaves little residue on the soil surface, which can lead to soil erosion and a long-term reduction in soil organic matter. Fields harvested for silage are also likely to have manure applied to them. Chopping and manure application requiring heavy equipment can lead to long-term soil compaction. These factors can contribute to less productive soils in the future, plus increased potential loss of nutrients after the manure application.
Cover crops help
While some farmers have already discovered the benefits of using cover crops after silage, many fields across the state are still left bare after harvest. Silage harvest allows for earlier seeding of cover crops. Consider planting a cover crop such as cereal rye at a higher rate — a bushel and a half, or about 90 pounds per acre of pure live seed — for additional biomass to help protect fields from erosion, reduce water runoff and build back some organic matter.
However, cereal rye can tie up nitrogen until later in the growing season. If a field is in continuous corn silage production, starter fertilizer will likely be needed.
The earlier planting window also allows for the earlier established cover crops to grow more biomass, which could be especially helpful if there is need for additional grazing forage or haylage for green chop in the spring.
Harvesting the cover crop might act as the termination method, but alternative methods such as herbicide or tillage will more likely be needed. Harvesting the cover crop as haylage may not do much to build back soil organic matter. However, the soil will be protected over the winter, and valuable nutrients will be scavenged if manure is applied.
Cereal rye, barley and triticale are cover crop options.
Cover crops after silage harvest are especially needed when manure applications are planned. The cover crops not only protect the soil from erosion and reduce runoff, but also help hold valuable nutrients from the manure, therefore improving nutrient use efficiency for your next commodity crop.
There has been lots of discussion about timing of cover crop establishment versus timing of manure applications. A growing cover crop will more quickly tie up available nutrients from manure. Use no-till or low-disturbance injectors for liquid manure applications into a growing cover crop. Michigan State University has done some work with seeding during manure application by adding the cover crops directly to the slurry in the spreader. If doing so, beware of planting the cover crop seed too deep. Surface applications of liquid or solid manure can be immediately followed by equipment with a cover crop seeder to lightly incorporate both manure and cover crop seed in one pass.
Use cover crops as a valuable tool to counteract erosion and runoff that can happen with silage. Be sure to have a cover crop plan, including seed selection, establishment and termination. The cover crop, along with proper manure application, allows the growth of a low-residue crop such as silage and still provides for a healthier soil environment.
Bailey is the state conservation agronomist with the Natural Resources Conservation Service in Indiana. He writes on behalf of the Indiana Conservation Partnership.