Nsalambi Nkongolo, Kent Schmidt, Shane Johnson, and Robert Paro. Lincoln University, GIS Laboratory, 307 Founders Hall, Jefferson City, MO 65102-0029
To better quantify the effect of land use type on gases fluxes, we monitored CO2, CH4 and N2O emissions from soils in a pasture, forest and in a corn and soybean fields at Lincoln University farms. The relationship between soil controlling factors and gases fluxes was also studied. Vented and static chambers of 0.30 m long and 0.20 m diameter were installed permanently since 2003 in the forest and grassland and at the beginning of each growing season in corn and soybean fields. The chamber top had a middle hole covered by a stopper and used for air vacuuming and sampling. Soil air samples for determinations of CO2, CH4 and N2O were collected at least twice a month from May to December. The sampling process consisted in closing the chamber two ventilation holes with rubber stoppers, collecting an air sample with a 50 ml syringe and storing it in a 200 ml Tedlar bag. Analysis of CO2, CH4 and N2O from air samples was done within two hours with a Shimadzu GC-14. Soil samples were collected for analysis of chemical and physical properties. Soil thermal properties were directly measured with KD2 probe. All soils acted as sources for CO2 and N2O and sinks for CH4 as follows: -CO2: Soybean > Corn > Forest > Pasture; - N2O: Soybean > Corn > Pasture > Forest and CH4 uptake: Forest > Corn > Pasture > Soybean. Soybean had the highest N2O emissions confirming that legumes may increase N2O emissions compared to non N2-fixing crops. CH4 uptake was highest in the forest. Soil thermal diffusivity (D) explained 61% of variability in CH4 uptake in soybean and 56% of variability in CO2 emissions in corn field. This study will provide useful information on soil controlling factors needed in predictive models of greenhouse gases emissions