Corn stover harvest changes soil hydrology and soil aggregation

In the United States, commercial-scale cellulosic-ethanol production using corn (Zea mays L.) stover has become a reality. As the industry matures and demand for stover increases, it is important to determine the amount of biomass that can be sustainably harvested while safe-guarding soil quality and productivity. Specific study objectives were to measure indices of soil hydrological and aggregate stability responses to harvesting stover; since stover harvest may negatively impact soil hydrological and physical properties. Responses may differ with tillage management; thus, this paper reports on two independent studies on a tilled (Chisel field) and untilled field (NT1995 field). Each field was managed in a corn/soybean (Glycine max [Merr.]) rotation and with two rates of stover return: (1) all returned (Full Return Rate) and (2) an aggressive residue harvest leaving little stover behind (Low Return Rate). Unconfined field soil hydraulic properties and soil aggregate properties were determined. Hydrological response to residue treatments in the Chisel field resulted in low water infiltration for both rates of residue removal. In NT1995 field, Full Return Rate had greater capacity to transmit water via conductive pathways, which were compromised in Low Return Rate. Collectively, indices of soil aggregation in both experiments provided evidence that the aggregates were less stable, resulting in a shift toward more small aggregates at the expense of larger aggregates when stover is not returned to the soil. In both fields, aggressive stover harvest degraded soil physical and hydrological properties. No tillage management did not protect soil in absence of adequate residue.