Stover Removal Affects No-Till Irrigated Corn Yields, Soil Carbon, and Nitrogen

Corn (Zea mays L.) stover removal can increase yields under no-till (NT) in climates where cold spring soil temperatures delay emergence and plant growth. The study objective was to evaluate partial stover removal (PR) effects on irrigated NT corn grain and stover yields, N uptake, and changes in soil organic carbon (SOC) and total soil nitrogen (TSN) compared to full stover retained (FR) under three N treatments on a clay loam soil. Stover removal (average 66%) increased early spring soil temperatures and enhanced early plant development compared to FR. Grain and stover yields increased with increasing N rate, as did plant N and C uptake, but varied with stover treatment. Averaged over N rate, grain yields were greater with PR than FR, but stover yields were lower with PR than FR. The C/N ratio of stover declined with increasing N rate. Nitrogen fertilization did not significantly influence SOC and TSN stocks aft er 7 yr. Averaged over N rates, PR removal decreased SOC 2.4 Mg SOC ha(-1), but FR increased SOC 6.8 Mg SOC ha(-1) in 0- to 30-cm soil depth. TSN stocks increased significantly with FR (1176 kg N ha(-1)) but not with PR (70 kg N ha(-1)). These results suggest that continued, long-term residue removal will negate any initial yield benefits from more rapid early spring plant development. Partial stover removal as a cellulosic feedstock at the levels we used for ethanol production would negatively impact soil quality under irrigated, NT corn production in Colorado.