Residue Removal Effects on Continuous Corn Production and Soil Quality Under Variable Nitrogen Rates and Tillage Systems.

Corn residue is an important component of soil carbon budget and development of soil quality indices. However, corn residue in recent years has been considered as another potential feedstock source for ethanol production in addition to or alternative to corn grain. The removal of corn residue, however, may require farmers to change their current tillage and fertilization practices to overcome potential declines in corn production and soil quality. The objective of this experiment was to examine corn grain yield response and soil quality  indices under no-tillage (NT) and conventional tillage (CT) (fall chisel-field cultivation prior to planting) and nitrogen fertilization rates of 0, 55, 110, 165, 220, and 275 kg N ha^-1 with variable rates of residue removal (0, 50, and 100%). Study was established in fall of 2008 on two sites, a poorly-drained soil at the Iowa State University Agronomy Research Farm (North central, IA) and a well-drained soil at the Armstrong Research and Demonstration Farm (Southwest, IA) in continuous corn. Expected findings include changes in soil total C and N, soil microbial biomass-C, bulk density, wet aggregate stability, and water infiltrations under different residue removal management practices. Additionally, a C budget approach was used to estimate net ecosystem productivity ((above-ground biomass + below-ground biomass) – microbial respiration). These measurements provide insights on whether these management practices were a sink or a source for soil C sequestration and atmospheric CO₂. Preliminary findings indicate no significant declines in corn grain yield when residue was removed. However, significant declines in soil quality properties were observed after only three years of residue removal. The severity of soil quality deterioration due to residue removal varied with different tillage and N managements.