Submitted to: Land Degradation and Development
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/31/2007
Publication Date: 1/15/2008
Citation: Starr, G.C., Lal, R., Owens, L., and Kimble, J. 2008. Empirical relationships for soil organic carbon transport from agricultural watersheds in Ohio. Land Degradation and Development. 19:57-64. Interpretive Summary: The issue of global climate change and its tie to carbon in the atmosphere increase the need to assess carbon sources and sinks. Carbon in soils can be stored with some agricultural practices while other practices cause some soil carbon loss. At the North Appalachian Experimental Watershed near Coshocton, Ohio, soil organic carbon (SOC) along with N, P, and K were measured in surface runoff from two small watersheds for 13 years. These watersheds were in a corn-soybean rotation under no-till and chisel-till. The loss of SOC in runoff, soil loss, runoff, N, P, and K are all mathematically linked, and the knowledge of one may give an assessment of another in specific watersheds and management practices. Often runoff or nutrient loss data are more readily available than SOC data, and they can be used to calculate an estimate of SOC loss. With this capability, land managers and policy makers can estimate the amount that SOC loss can be reduced with appropriate changes in agricultural practices, thus reducing agriculture's "carbon footprint".
Technical Abstract: Improved quantification is needed for long-term soil organic carbon (SOC) transport in runoff at watershed scales. Coshocton wheel samplers were used to collect runoff samples from no-till and chisel-till watersheds in corn (Zea mays) and soybean (Glycine max) rotations over 13 years. Samples were analyzed for SOC, N, P, K, and soil losses. The SOC losses, ranging from 0 to 357 kg ha-1 event -1, were correlated (r2=0.80-0.94) in power law relationships with N, P, K, soil loss, and runoff. Two events occurring in corn when soybean and cover crop residue were present in no-till had combined SOC transport of 460 kg ha-1, nearly double the no-till losses of a previous 11-year period and 20 times higher than chisel-till in the same events. Infrequent, extreme transport events that are not well characterized empirically, particularly in no-till, can strongly influence hydrologic C transport from agriculture watershed.