Soil Available Nitrogen Uptake Under Cover Crops in Illinois.

Nitrogen scavenging is a widely documented benefit of many types of winter cover crops (WCC). Highly mobile soil available N can pose major problems to waterways, as well as direct economic losses to the grower. Therefore, implementation of WCCs can utilize that residual N and the subsequent decaying organic matter can be used by the cash crop. This goal of this study is to monitor soil available N uptake from six different cover crop treatments throughout the state of Illinois. The experimental design was a split-block in an RCB design with four replications within each phase of the corn-soybean rotation. Two levels of tillage were present, chisel plow and no-till. Cover crop treatments had six levels, differing based on the following cash crop. Hairy vetch [Vicia villosa] and red clover [Trifolium pretense] occur as treatments only in plots preceding corn [Zea mays], with cereal rye [Secale cereal] and spring oats [Avena sativa] growing only before soybean [Glycine max] crops.  The effects of rapeseed [Brassica napus], daikon radish [Raphanus sativus], and annual ryegrass [Lolium multiflorum] will be tested before both corn and soybean, along with an unseeded control plot.  Preliminary results indicate that a substantial amount of nitrate exists during the fall and spring seasons, with more variability occurring after the corn phase of the corn-soybean rotation. Following corn, approximately 35 lbs/acre of nitrates were recorded in the top two feet of soil during the fall of 2013. Fall of 2014 showed about 15 lbs/acre of nitrates for both the corn and soybean fields over the entire three foot soil profile. Results indicate that the overall soil profile contained similar nitrate values for barren control plots compared to cover crop rotations. However, during the spring and fall of 2013, rotations containing cereal rye reduced soil nitrates.