Removal of plant residues from agricultural land for cellulosic energy or otherwise will necessarily require management for protection of plant and soil productivity. This study was conducted to determine whether residue removal of potential biomass crops over a range of crop productivity regimes would impact plant and soil productivity. The effects of crop productivity regimes, cultivation of four biomass crops, and the removal of plant residues were investigated in Prosser, WA on a Warden Silt Loam (Coarse-silty, mixed, superactive, mesic Xeric Haplocambids).

            In 2007, corn (Zea mays L.), wheat (Triticum aestivum, L.), switchgrass (Panicum virgatum L., SG), and grass polyculture (POLY) comprised of SG, eastern gamma grass (Tripsacum dactyloides), big bluestem (Andropogon gerardii), and Illinois bundleflower (Desmanthus illinoensis) were established as potential biomass crops under three levels of net primary productivity (NPP) and plots were split with removed (RR) or not removed (NR) plant residues. In 2008 and 2009 Corn and wheat production was as expected. In 2008 SG and POLY yields were typical of perennial establishment. In 2009 SG and POLY yields rose to 5.3 to 43.6 Mg ha^-1 yields. Ethanol conversion of biomass yield revealed SG and POLY as competitive in 2008 and significantly greater producers of ethanol in 2009. Fluorescein diacetate (FDA), soil C mineralization, total soil organic carbon (SOC), and stable carbon isotope analysis were utilized in comparison of feedstock crops. Although FDA was not, C mineralization proved to be a sensitive indicator of microbial activity in response to treatment effects. Although total SOC did not detect changes, significant crop and residue removal effects were detected by analysis of SOC pool dynamics. Corn and wheat RR decreased C mineralization and SOC dynamics while NR increased them. Switchgrass RR and NR significantly increased C mineralization and improved SOC dynamics.