Effect of Fall Nitrogen on Corn Residue Breakdown in Illinois.

There are challenges in continuous corn production in no-till systems due to high volumes of crop residue. A practice in Illinois is to apply nitrogen (N) in the fall to aid residue decomposition. There is limited research to determine the effectiveness of such practice. A two-year study near Urbana, Illinois investigated residue decomposition and stalk integrity of corn residue placed in mesh bags under no-till. The N treatments were liquid ammonium sulfate (21-0-0) and urea-ammonium nitrate (32-0-0) broadcast-applied in September, October and November at a rate of 34 kg ha^-1. Stalk strength was measured from September until June using a push penetrometer. Across treatments, stalk strength decreased by 21% for the first year and 51% for the second year between late September and April 1. Residue from 2012 was weaker than 2011, possibly due to drought conditions. In 2012, by April 1, fall application of N, averaged across application time, reduced stalk strength by 12% relative to treatments receiving no N, but no decrease was observed by April 1, 2013. Treatments receiving N in September showed no differences in stalk strength relative to treatments receiving later N applications. Carbon-to-nitrogen ratios of residues were not significantly different among years and treatments. Results indicate that applying N in the fall to enhance decomposition is not warranted.