Corn Nitrogen Fertilization Requirement and Corn-Soybean Productivity with a Rye Cover Crop

Winter rye (Secale cereale L.) cover crop (RC) has potential to reduce NO3-N loss from corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] fields. However, RC effects on annual crop productivity and corn optimal N fertilization requirement are unclear. The objectives were to evaluate corn and soybean yield response to RC and corn optimal N rate. Treatments were no-RC and RC with six fertilizer N rates (0-225 kg N ha(-1)) applied to corn in a no-till corn-soybean (CS) rotation at four Iowa sites in 2009 through 2011. The RC biomass and N uptake was low, with a maximum of 1280 kg dry matter (DM) ha(-1) and 26 kg N ha(-1), respectively. In the no-N control, the RC reduced soil profile NO3-N by 15 kg N ha(-1) only at time of RC control before corn planting. Corn canopy sensing, plant height, and plant population indicated more N stress, reduced plant stand, and slower growth with RC. The RC reduced corn grain yield by 6% at the economic optimum N rate (EONR). The EONR was the same with no-RC and RC, but plant N uptake efficiency (PUE) was reduced at low N rates with RC, but not above the EONR. Soybean yield was not affected by RC. Results indicate N fertilization rate should be the same with or without RC. Improvement in RC systems and management could make RC a more viable practice within no-till corn and soybean production.