Winter Cover Crops Impact on the Distribution of Soil Inorganic Nitrogen Following Fall Applied Anhydrous Ammonium.

The inclusion of cover crops into a spring applied nitrogen (N) system has been shown to improve nitrogen efficiency, while maintaining crop yields. However, minimal research has been conducted on the influence cover crops have on fall applied N. Therefore, the objective of this research was to determine the efficacy of winter cover crops to impact the distribution of soil inorganic N following fall applied anhydrous ammonium.  The experimental site is located at the Illinois State University Research farm in Lexington, IL.  The treatments consisted of a control and two cover crop treatments, tillage radish and cereal rye. All treatments received a fall application of 200 kg N ha^-1 in the form of anhydrous ammonia. Soil samples were collected in the spring at four separate depths and were analyzed for inorganic N. At the 0-5cm depth, we determined that tillage radish resulted in significantly (P<0.05) greater soil NO₃-N relative to the control and cereal rye treatments.  The control had 48% greater NO₃-N compared to the cereal rye treatment at the agronomic depth of 5-20cm.  In the environmental depth of 20-80cm, we observed that fall applying N into a living cover crop resulted in 48% (Cereal Rye) and 29% (Tillage Radish) less soil NO₃-N when compared to the control. Over a three year period, winter cover crops reduced nitrate leaching and stabilized a greater concentration of soil NO₃-N in the agronomic depths, relative to the control, following fall applied N.