Nitrogen Rate Optimization for Grain Yield Within Fall and Spring Applications and Cover Crop Systems,.

Proper nitrogen (N) management and recommendations have proven to be challenging due to the dynamics of N transformations within the soil environment.  Multiple studies have indicated that incorporating proper N rates and timing improves N efficiency while maintaining optimal yield; however, little is known about influence of cover crops on N optimization in Central Illinois.  Thus, the objective of this study were i) to investigate  the optimal nitrogen rates within the fall and spring application timing for  corn and soybean yield, ii) determine the combined impact of N rate, timing, and cover crop inclusion on N use efficiency and iii) quantify natural mineralization of soil N excluding N fertilization, with and without cover crops..  The location site for this experiment was the Illinois State University farm in Lexington, IL.  Treatments included timing of N (spring sidedress versus fall), N rates (0, 56, 112, 168, and 224 kg ha^-1), and the inclusion of cover crops (radish, rye, and clover).  Soil samples were collected in the fall before N treatment and in the spring prior to planting at four depths to 80 cm and were analyzed for nitrate and Total N.  Plant tissue samples will be collected at V6, V12, and VT to calculate total N through the growing season.  Grain yield will be calculated to 15.5% moisture upon harvest in the fall.  The results from this study will indicate the effectiveness of varying N rates timing, and cover crops on N efficiency and corn yield and quantify the impact of cover crops on the contribution of naturally mineralized N to the available N pool.