Stover Harvest and Tillage System Effects on Corn Response to Fertilizer Nitrogen

Demand for corn (Zea mays L.) stover is increasing for livestock and bioenergy production. Excessive stover harvest (SH) could impact crop productivity and soil N cycling. A 3-yr study was conducted at two Iowa sites with continuous corn to determine the effect of SH level and tillage system on grain yield, response to N fertilization, and optimal N rate. Treatments were none, partial, and complete SH, chisel plow tillage and recently implemented no-till, and six N rates from 0 to 280 kg N ha(-1). Profile soil NO3-N concentration (with no fertilizer N) increased slightly from spring preplant to early June only with no SH but were the same with all SH levels after corn harvest. Corn canopy normalized difference vegetative index (NDVI) values were greatest with both SH levels and chisel plow. Increases in NDVI due to SH was less with chisel plow than no-till. Corn grain yield was 9% (0.84 Mg ha(-1)) greater with chisel plow than with no-till. At the economic optimum N rate (EONR), grain yield was not influenced by SH with chisel plow but was 6% greater with each SH level under no-till. The EONR was the same with both tillage systems but was 22 and 45 kg N ha(-1) lower with partial and complete SH, respectively, than no SH. Results of this study indicate the potential for increased corn yield with SH in a no-till system and a reduced fertilizer N rate requirement with SH regardless of tillage system.