Influence of Biochar and Diversified Cropping Systems on Soil Physical and Chemical Properties.

Corn residue removed from Midwestern farms is the largest potential source of biomass for cellulosic bioenergy production in the U.S. Long-term harvesting of biomass, however, may lead to the degradation of soil and water quality unless new management practices are used to increase carbon inputs to soils. Alternative cropping systems that include perennial grasses, small grains and biochar amendments may help reduce the negative effects of biomass harvesting on soil quality. A long-term crop rotation and biomass harvesting experiment was established in 2006 to evaluate multiple bioenergy crops (corn stover, triticale and switchgrass) in diversified cropping systems and the impact of non-traditional rotations with and without biochar on soil quality. In 2014, intact soil cores were collected and analyzed for: solute transport, saturated hydraulic conductivity, bulk density, porosity, pH, EC, total C, total N, and C/N ratio. Chemical breakthrough curves, quantified by changing the concentration of a leaching CaCl₂ solution, and measuring EC of the effluent, indicate that biochar amendments and non-conventional crop rotations have minimal effects on ion transport relative to controls. Across all crop rotations there was an increase in total soil C, soil C/N ratio, pH, EC, and gravity drained water content, and a decrease in bulk density for soils treated with biochar relative to no-biochar controls. Saturated hydraulic conductivity was strongly influenced by both crop rotation and age of biochar. The results suggest that soil biochar amendments and more diverse crop rotations may help mitigate some of the adverse effects of biomass harvesting on soil quality.