Multiple corn stover removal rates for cellulosic biofuels and long-term water quality impacts

Abstract

The objective of this work was to quantify the long-term runoff, percolation, erosion, and losses in nitrate-nitrogen, total phosphorus and pesticides attributed to multiple levels of corn stover (Zea mays L.) removal. A field-scale modeling framework, which utilized the Groundwater Loading Effects of Agricultural Management Systems/National Agricultural Pesticide Risk Analysis (GLEAMS–NAPRA) model and the Revised Universal Soil Loss Equation, Version 2 (RUSLE2), was created and applied within Indiana to evaluate water quality impacts associated with three corn stover removal rates (38%, 52.5%, and 70%), based on proposed harvest efficiencies of three multipass field collection systems, with two tillage options (fall chisel/spring disk and no-till). The model results suggest that removing corn stover at the rates 38% (2.40 to 3.19 t ha⁻¹ [1.07 to 1.42 tn ac⁻¹]), 52.5% (3.32 to 4.41 t ha⁻¹ [1.48 to 1.97 tn ac⁻¹]) and 70% (4.42 to 5.88 t ha⁻¹ [1.97 to 2.63 tn ac⁻¹]), with no-till practices, would result in statistically significant higher annual erosion losses (p < 0.05), when compared with no residue removal management. On soils with 4% or less slopes, a 70% residue removal rate—4.4 to 5.9 t ha⁻¹ (1.96 to 2.63 tn ac⁻¹)—with no-till practices, would result in slightly lower erosion losses when compared with conventional tillage involving no residue removal. No-till systems produced higher total phosphorus losses when commercial fertilizer was surface applied as opposed to the incorporation method practiced with conventional till-age. However, levels of leached nitrate-nitrogen from no-till systems were significantly lower than losses from conventional tillage, partly due to lower mineralization processes associated with nutrient cycling. The results point to the necessity of establishing new sets of regional soil and water conservation criteria that would include harvesting unprocessed agricultural residue following corn-grain harvest to meet biofuel demands.