Soil Quality Associated with Biofuel Crop Management.

Interest in production of various crops as potential sources of biofuels motivated research to develop optimum nutrient management while maintaining or improving soil quality. Eight biofuel cropping systems were evaluated during 2008 – 2012 at two locations in northeast Missouri on Mexico silt loam (fine, smectitic, mesic Vertic Epiaqualf). Three fertilizer regimes were followed using recommendations based on standard soil tests or crop removal values. Soils collected (15-cm depth) each fall were analyzed for soil fertility, and soil quality indicators (organic C, total N, aggregate stability, soil enzyme activities). Over the four-year study, aggregate stability increased greatest under switchgrass, miscanthus, and the sweet sorghum-wheat double crop; lowest values were consistently detected under continuous corn and corn-soybean rotation. Organic C and total N increased slightly with highest contents found for switchgrass and miscanthus. Soil enzymes, representing biological activity, greatly increased under switchgrass, miscanthus, and sweet sorghum-wheat by up to 100% for dehydrogenase and ß-glucosaminidase whereas corn-based systems showed only slight increases. Fertilizer regime had little effect on soil quality indicators. Results suggest that perennial crops or a double-crop system can be managed as potential biofuel feedstocks with no adverse effects on soil quality based on the indicators assessed in this study.