Grassland canopy management and native tallgrass species composition effects on C and N in grass canopies and soil

Abstract

Grassland canopy management (spring burn, mowing and residue removal in late-summer, or no management) and native tallgrass species composition (cool season mixture, warm season mixture, or combined cool and warm mixture) effects on C and N in aboveground biomass and soil were investigated at Brookings SD on a previously-plowed Barnes clay loam (fine-loamy, superactive, frigid Calcic Hapludoll). During the last 2 yr of the 9-yr experiment, shoot biomass was affected by canopy management with the burn (2,730 kg ha−1) and mow (3,421 kg ha−1) treatments containing less than no management (4,655 kg ha−1). Burn treatment biomass contained 1,189 kg ha−1 and 25 kg ha−1 of C and N, mow contained 1,433 kg ha−1 and 33 kg ha−1 of C and N, while no management contained 2,014 kg ha−1 and 39 kg ha−1 of C and N, respectively. Soil C accumulation was independent of grass species composition. Soil C accumulation rates, which increased in strong linear fashion (r2 of 0.89 to 0.92) after initial grass establishment, were 387 kg C ha−1 yr−1, 503 kg C ha−1 yr−1, and 711 kg C ha−1 yr−1 for burn, mow, and no management treatments, respectively. Thus, grassland management methods used after conversion of cropland to grassland have important effects on grass biomass and soil C accumulation.