Submitted to: Plant and Soil
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 25, 2010
Publication Date: April 7, 2010
Citation: Riedell, W.E., Osborne, S.L., Schumacher, T.E., Pikul Jr, J.L. 2010. Grassland Canopy Management and Native Tallgrass Species Composition Effects on C and N in Grass Canopies and Soil. Plant and Soil Journal. DOI 10.1007/s11104-010-0341-2. Interpretive Summary: Grassland management techniques that affect forage production may also potentially affect soil organic carbon. Despite the importance of grassland management in maintaining productivity, relatively little information is available that quantitatively describes the effects of long-term management options on soil organic carbon. More effective management of grassland that has been converted from cultivated cropland will require a better understanding of the effects of fire and mowing on grassland biomass productivity and soil characteristics. There currently are 1.2 million hectares in South Dakota and Minnesota enrolled in Conservation Reserve Program. This region is also slated to provide cellulosic feedstocks for biofuels. Thus, scientific inquiry on management options for native grass mixtures planted into previously-cultivated cropland and the effects these management options have on soil organic carbon are important priorities. This study was conducted to measure the effects of grass canopy management treatment (burning in early spring, mowing and residue removal in mid- to late-summer, or no management) and native grass species composition (mixtures of cool season species, warm season species, or combined cool and warm season species) on soil and grass canopy carbon and nitrogen in cropland recently converted to grassland. This experiment reveals that grassland management treatments (annual spring burning, late summer haying, and no management) and grass species composition treatments (cool season, warm season, and cool+warm season mixtures) had important independent and interactive effects on biomass production as well as on C and N in grass canopies and soil in previously row-cropped plots that were converted to perennial native grasses. While soil C accumulation appeared to be independent of the grass species composition of the plots, methods used to manage grass canopies had significant effect upon the rate of soil C accumulation during the first 9 years after grass plot establishment. In this context, the choice of grassland management methods when converting cropland to grassland should be based upon consideration of grass biomass utilization as well as soil C accumulation.
Technical 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 (2730 kg ha-1) and mow (3421 kg ha-1) treatments containing less than no management (4655 kg ha-1). Burn treatment biomass contained 1189 and 25 kg ha-1 of C and N, mow contained 1433 and 33 kg ha-1 of C and N, while no management contained 2014 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, 503, and 711 kg C ha-1 yr-1 for burn, mow, and no management treatments, respectively. These results suggest that grassland management methods used when converting cropland to grassland have important effects on grass biomass and soil C accumulation.