Monday, November 13, 2006
47-8
Soil Thermal Properties and CO2, CH4 and N2O Emissions from a Pasture in Missouri.
Shane Johnson and Nsalambi Nkongolo. Lincoln Univ, Jefferson City, MO 65102-0029
Agricultural systems are sources and sinks for greenhouse gases. To quantify the net effect of these systems on the atmospheric concentration of greenhouse gases, amounts of fluxes from soil must be known and the relationship between gas flux and soil controlling factors need be understood. The objectives of this study were (1) to quantify the amounts of CO2, CH4 and N2O fluxes from soil in a pasture; and (2) to assess the relationship between CO2, CH4 and N2O fluxes and soil thermal conductivity (K), resistivity (R) and diffusivity (D). The study was conducted in a permanent pasture at Lincoln University’s Washington Carver farm. Soil samples were collected for analysis of chemical and physical properties and direct measurement of soil thermal properties were conducted every two weeks for 4 months. Analysis of CO2, CH4 and N2O from air samples was done within two hours of sampling at Dickinson Research Center with a Shimadzu Greenhouse Gas GC-14. Results showed that CO2 ranged from 19.26 to 173.62 mg CO2-C m-2 h-1, CH4 uptake from 19.60 to 27.76 ug CH4–C m-2 h-1 and N2O from -4.01 to 238.26 ug N2O-N m-2 h-1. N2O, CO2, and CH4 had logarithmic and polynomial correlation with soil temperature, with correlation coefficients (r) ranging from 0.30 to 0.40. N2O also correlated with K, R, and D. The results suggest that soil thermal properties may be important controlling factors for greenhouse gas fluxes from soils.