Producers should also consider leaving more of the stalk standing after harvest. Paul Jasa recommends leaving stalks 12 to 18” tall when the succeeding crop will be planted between the corn rows without tillage. The taller stalks will increase air movement down the row and increase decomposition rates. If the planting equipment is configured properly, the coulters, openers, gauge wheels and press wheels will pass between the old corn rows and will not have to contend with the standing stalks. However, the taller stalks may catch on planting equipment in the spring. (See Photo 1, below)
There is a theory that fall applications of nitrogen will increase stalk decomposition rates. The theory is based on the process of nitrogen immobilization. Corn stalks have a very high carbon to nitrogen ratio so they are an excellent source of food and energy for microbes. However, the low nitrogen content may limit microbe population growth as nitrogen is required to build new cells. If additional nitrogen is applied in the fall, microbial populations and residue breakdown could potentially increase. Research has not shown this to be the case in the northern Corn Belt. Low temperature is the limiting factor to microbial decomposition and not soil nitrogen. Therefore, fall applications of nitrogen fertilizer are not recommended.
Harvesting the residue as a biofuel crop or for livestock feed effectively solves planting equipment challenges and provides additional income. However, it exposes the soil to wind and water erosion and removes essential crop nutrients and carbon which is critical to maintaining soil quality and productivity. Livestock producers have the ability to replace these nutrients through manure applications. Cash crop producers can replace the nitrogen (17 lbs./ton), phosphorus (4 lbs./ton) and potassium (50 lbs./ton) removed in the residue by purchasing and applying commercial fertilizers. Replacing the carbon removed in the residue without manure applications is much more difficult.
MSU Extension specialists and educators have several research, education and demonstration projects planned for 2012 to help Michigan producers identify and implement residue management practices that improve farm income and conserve soil resources.
This article was produced by the SMaRT project (Soybean Management and Research Technology). The SMaRT project was developed to help Michigan producers increase soybean yields and farm profitability. Funding for the SMaRT project is provided by MSU Extension and the Michigan Soybean Checkoff program.