In Field Measurements Of Nitrogen Mineralization Following The Termination Of Cover Crops.

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 chemical 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, crimson clover and control (no cover crop).   Cover crops were sampled and analyzed for total nitrogen to calculate N-uptake. After chemical termination soil samples were collected weekly and were analyzed for nitrate to determine the rate of nitrification. Cereal rye and crimson clover did not have a significant impact on rate of soil nitrification.  In spring 2012, tillage radish had a rate of nitrification two times greater than the control.  In 2013 radish rate of nitrification was not significantly greater than the control. It is likely that rate of nitrification is strongly driven by spring weather.  Spring 2012 was considerably warmer and had less precipitation than 2013; warm/dry weather likely contributed to greater mineralization of radish biomass and soil nitrification.  None of the cover crop treatments negatively impacted spring nitrification; radish increased nitrification and soil nitrate immediately before corn planting. On average radish releases more fall applied N relative to cereal rye or crimson clover.  The inclusion of cover crops into conventional cropping systems has the potential to improve the efficiency of fall applied N.