Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 14, 2002
Publication Date: January 1, 2003
Citation: Franzluebbers, A.J., Stuedemann, J.A. 2003. Bermudagrass management in the southern piedmont usa. iii. particulate and biologically active soil carbon. Soil Science Society of America Journal. Interpretive Summary: The effect of forage management strategies on carbon cycling is of importance to the understanding of greenhouse gas emissions, agronomic productivity, and changes in soil quality. Particulate organic carbon consists of large pieces of roots and plant residues that may be partially decomposed. This pool of organic matter is important for the development of fwater-stable aggregation, which improves the soil rooting environment and helps to reduce soil erosion. Biologically active pools of organic matter are important for nutrient cycling and the conversion of plant materials into soil organic matter. Soils rich in organic matter offer plants nutrients throughout the growing season and help to reduce atmospheric carbon dioxide. We evaluated several grass management systems during four years for their effects on soil organic matter pools. Whether fertilization was from organic or inorganic sources had no effect on organic matter pools. Cattle grazing systems resulted in twice the accumulation of particulate and biologically active carbon pools than did unharvested grass or grass that was harvested for hay. Cattle enhanced soil organic matter pools by returning undigested plant materials back to the soil.
Technical Abstract: Particulate organic carbon (POC), soil microbial biomass carbon (SMBC), and potential carbon mineralization (CMIN) were evaluated during four years on a previously eroded site dominated by Typic Kanhapludults in response to factorial combinations of N fertilization strategy (inorganic only, crimson clover cover crop plus inorganic, and broiler litter) and forage harvest strategy (unharvested, low and high grazing pressure, and hayed, which represented a gradient from low to high utilization). Accumulation of POC, SMBC, and CMIN with time was greatest at a depth of 0 to 2 cm and was not different among fertilization strategies. To a depth of 6 cm, POC accumulated at a rate of 650-730 kg/ha/year under unharvested or hayed strategies and at a rate of 1360-1440 kg/ha/year under cattle grazing strategies. Accumulation rate of SMBC was also dependent upon forage utilization intensity, averaging 51, 96, 119, and 74 kg/ha/year under unharvested, low grazing pressure, high grazing pressure, and hayed strategies, respectively. Particulate and biologically active soil carbon pools improved under all forage management strategies, although cattle grazing imparted the greatest improvement due to return of feces to soil.