Effects of Winter Cover Crops on Nitrogen Use and Performance of Soybean and Corn.

Corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] are the most important annual crops in the U.S. Corn Belt and have been successfully grown in rotation in the region. Concerns about the excess use of nitrogen in the system and its impacts on environmental quality of the environment call for sustainable cropping practices. The integration of cover crops in the rotation is considered an effective strategy for sustainable production. A 3-yr field experiment was established in southwest Minnesota to study the effect of winter cover crops on soil nitrogen and its impact on growth and yield of corn and soybean. Field pennycress (Thlaspi arvense. L.), winter camelina (Camelina sativa L. Crantz), and winter rye (Secale cereale L.) were used in a soybean-corn rotation. Nitrogen use and efficiency of cover crops and primary crops, as well as the effect of cover crops on soil N and its impact on the following crop were assessed. Our preliminary results indicate that the cover crops ability to scavenge N was marginal in the fall but significant in the spring, mainly for winter rye. Within the primary crop, none of the winter cover crops had significant effect on N use, growth or grain yield of corn and soybean, evidencing their potential use in the rotation of these important crops in the region.