Effect of the Spatial Variability of Fluxes On Total Field Greenhouse Gases Emissions.

Despite numerous studies, uncertainty still exist in the quantification of greenhouse gases emissions because of their spatial and temporal variability. We quantified total CO₂, CH₄ and N₂O fluxes from soil in a corn and soybean field using two calculation methods: A traditional method (TA) based on statistical mean and field area and Geographic Information Systems (GIS) approach using classified maps. The study was conducted at Lincoln University’s Freeman in Jefferson City, Missouri. Soil air samples were collected between 7:00 and 10:00 a.m every two weeks from August to October 2011. Concentrations of CO₂ from soil air samples were measured with a Shimadzu GC-2014 gas chromatograph. Flux values for the TA method were calculated by multiplying the field average flux by the field area. For the GIS approach, maps of CO₂, CH₄ and N₂O were produced using ARCGIS 10-Geostatistical Analyst Extension with the inverse distance weighing (IDW) as the interpolation method. Maps were later classified using Multispec 3.2 and total flux computed. The comparison of both methods showed an underestimation of flux values calculated with the TA method. The GIS approach offer a promise for quantifying gas flux from soil in agricultural fields.