David W. Archer, Northern Great Plains Research Laboratory, USDA-ARS, Mandan, ND, Mark A. Liebig, PO Box 459, USDA-ARS, Mandan, ND and Scott L. Kronberg, USDA-ARS, Northern Great Plains Research Laboratory, Mandan, ND
Limited data are available on crop productivity and economic effects of harvesting crop residues for biofeedstocks or livestock feed in the semi-arid plains. A Bioenergy Cropping Systems (BCS) study was initiated in fall 2008 to investigate removal effects on crop production, environmental outcomes, and economic returns. Treatments include three crop rotations: spring wheat (Triticum aestivum L.)-dry pea(Pisum sativum L.), WP; spring-wheat-dry pea/cover crop mix, WP/CCM; spring wheat-dry pea-corn (Zea mays L.), WPC; and four biomass removal treatments: no biomass removal, NONE; harvest and remove wheat straw, WHARV; harvest and remove residues from each crop, ALLHARV; and graze all crop residues, ALLGRZ. This analysis focused on short-term (2010-2012) effects of treatments on crop productivity and economic returns. Treatment effects on yields and net returns varied among years. Residue removal significantly affected wheat yields in 2010 and 2012, and corn in 2012. Wheat yield in 2010 for ALLHARV was higher than ALLGRZ, but in 2012 was higher for NONE and ALLGRZ than WHARV and ALLHARV. Corn yield in 2012 for NONE was higher than WHARV and ALLHARV. Rotation and biomass removal treatments affected net returns in all years, except for biomass removal in 2012. Net returns were highest for WPC in all years. Net returns for ALLGRZ were significantly higher than NONE and ALLHARV in 2010 and 2011, respectively. Breakeven biomass prices for mechanical harvest to be profitable relative to NONE ranged from $31 Mg-1 for WHARV in WP to $212 Mg-1 for WHARV in WPC, and breakeven grazing values ranged from $0.26 per grazing day in WP to $0.34 in WP/CCM. Continued monitoring is planned to identify long-term effects of biomass harvest on soil characteristics and resulting impacts on crop productivity and economic returns.