Synchronizing of the Mineralization of Cover Crops with Corn Growth Stages

 

 

The ability of cover crops to scavenge nitrogen from the soil during winter months has been thoroughly investigated, however little is known about the mineralization rate of cover residue or the rate of scavenged N release back to the soil solution via nitrification. Therefore, the objective of this study is to determine the impact of cover crop species on the release of fall N to the spring cash crop following termination. The experimental site was located at the Illinois State University Research and Teaching farm in Lexington, IL.   All treatments received fall nitrogen at a rate of 200 kg ha-1 into standing cereal rye, tillage radish, radish/rye, and control (no cover crop).   Cover crops were sampled and analyzed for total nitrogen to calculate N-uptake. After termination soil samples were collected biweekly and were analyzed for nitrate and ammonium at the agronomic depth to determine the rate of nitrification.  In spring 2013, tillage radish had a nitrate concentration almost two times greater than the control and the cereal rye at the V6 corn growth stage.  The V8-V11 growth stages are crucial to obtain maximum yield and in the spring of 2013 the tillage radish had 392% more nitrate in respect to the control, the radish/rye mixture had 227% more nitrate than the control, and the rye on had 118% more nitrate than the control.  It is likely that rate of nitrification is strongly driven by spring weather.  None of the cover crop treatments negatively impacted spring nitrification; radish increased nitrification and soil nitrate immediately before corn planting and throughout the growing season. On average radish and the radish/ mixture release more fall applied N relative to cereal rye.  The inclusion of cover crops into conventional cropping systems has the potential to improve the efficiency of fall applied N.