Management Options for Increasing Soil Organic Carbon in Corn-Alfalfa Rotations.

Managing cropping systems to sequester soil organic carbon (SOC) improves soil health and a system’s resiliency to impacts of changing climate. Our objectives were to 1) monitor SOC from a bio-energy cropping rotation in central Pennsylvania that included a corn-soybean-alfalfa rotation (CSA), switchgrass, and reed canarygrass; 2) use CQESTR, a process-based soil C model, to predict SOC in the bioenergy rotation with projected changes in climate; 3) to simulate the changes in SOC with no-till (NT), cover cropping, and manure application for a corn-alfalfa rotation (CA); and 4) predict impacts of NT and corn stover removal in a corn–soybean rotation (CS) over 40 years. Simulated and measured data in all depths were significantly (p<0.001) correlated. Simulations with multiple management options for CA indicated NT increased SOC, while cover crops and liquid manure application had little impact on SOC (probably due to relatively low organic solids content of liquid manure and limited biomass from the cover crop). Carbon sequestration was always greater in CA compared to CS, regardless of tillage. Tillage in CS lead to soil C losses over the 40 years, while NT maintained SOC levels over the 40 year simulation. Stover removal reduced SOC in the upper 10 cm by 13 and 48%, respectively, with 50 and 100% removal, but manure application partially countered that reduction. Overall, simulations suggest that NT corn production and inclusion of the perennial alfalfa provides the greatest potential for SOC sequestration on a typical central Pennsylvania farm.