Kyoung Ro1, Melvin Johnson1, Jeffrey M. Novak2, James Frederick3, and Donald Watts4. (1) USDA-ARS, 2611 West Lucas Street, Florence, SC 29501-1241, (2) USDA-ARS-Coastal Plains Research Center, 2611 W. Lucas St, Florence, SC 29501-1241, (3) Clemson University Pee Dee Research & Education Center, 2200 Pocket Road, Florence, SC 29506, (4) USDA-ARS,Coastal Plains Research, 2611 West Lucas Street, Florence, SC 29501
Soil properties such as particle size, soil organic carbon (SOC) and moisture contents, tillage operations and crop management practices influence greenhouse gas emission or consumption patterns from agricultural lands. Greenhouse gas (GG) emissions have been measured on small field plots, although minimal information is available on a landscape-scale. The objective of this research was to identify spacial differences in GG emissions and measure their fluxes from two 3.5-ha fields. The fields contain both well-drained upland and poorly-drained depressional soils in the middle Coastal Plain region of South Carolina. An optical remote sensing (ORS) technique was used to identify the regions of high GG concentrations. The ORS system included open-path tunable diode lasers for CH4 and CO2 gas measurements, controlled by an automatic positioning device, to receive laser reflections from nine retroreflectors. The ORS system measured path-integrated concentrations (PICs) of the test fields, which were then used to generate concentration contour diagrams via new horizontal radial plum mapping (HRPM) computer algorithms. For ground truthing, fluxes of GG (i.e., CO2, CH4, and N2O) from multiple points across the test fields were also measured using a static flux chamber and a photoacoustic multigas analyzer. Sulfur hexafluoride was injected to estimate ventilation rate of the static chamber. Contour diagrams of the GG fluxes were generated and were compared with the contours of SOC and moisture contents. The effects of rainfalls and different tillage operations (both conservation and conventional) on the GG flux were also studied.