Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/16/2005
Publication Date: 8/4/2005
Citation: Franzluebbers, A.J., Stuedemann, J.A. 2005. Bermudagrass management in the southern piedmont USA. VII. Soil-profile organic carbon and total. Soil Science Society of America Journal. 69:1455-1462.
Interpretive Summary: Organic carbon and nitrogen in soil are important components for maintaining soil fertility. Accumulation of organic carbon in soil is also a mechanism that helps to reduce carbon dioxide concentration in the atmosphere. Various land management systems have the potential to remove carbon from the atmosphere through photosynthesis and storage it as organic matter in soil. By providing more carbon from photosynthesis than carbon output from decomposition, soils can sequester carbon and help mitigate the greenhouse effect. Researchers at the USDA-Agricultural Research Service in Watkinsville, GA measured soil organic carbon and nitrogen at the end of five years of different pasture management systems and found that sequestration of carbon and nitrogen occurred primarily in the surface foot of soil. However, their ability to detect significant changes deeper in soil was hampered by higher natural variability and lower concentrations. Farmers, scientists, and environmental organizations can benefit from this information to guide more effective sampling strategies and to acquire better estimates of soil carbon sequestration with cattle grazing systems. Policy makers need this information to design effective strategies to mitigate rising CO2 in the atmosphere.
Technical Abstract: Estimates of potential soil C and N sequestration at depths below the traditional plow layer (i.e., 0-30 cm) in agricultural management systems are limited, but are needed to improve our understanding of management influences on nutrient cycling and potential greenhouse gas emissions. We evaluated the effects of N fertilization and harvest strategy on soil-profile distribution of organic C and total N during the first five years of 'Coastal' bermudagrass management. A significant increase in soil organic C and total N contents with time was detected to a depth of 0.6 and 1.5 m with inorganic fertilization, to a depth of 0.3 and 0.3 m with clover+inorganic fertilization, and to a depth of 0.15 and 1.5 m with broiler litter fertilization, respectively. Soil organic C and total N sequestration were significant to a depth of 0.9 and 1.5 m with low grazing pressure and to a depth of 0.6 and 1.5 m with high grazing pressure, respectively. This study illustrates that cattle grazing systems in the southeastern USA are capable of sequestering significant quantities of C and N in soil, but primarily at the soil surface.