Do Tillage Treatments Affect the Relationship Between Gas Fluxes and Soil Thermal Properties?.

Greenhouse gases (GHG) including carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) are naturally emitted from soils, but agricultural practices have been suggested to increase the flux of these gases from soil. We studied the effects of no-tillage (NT) and conventional tillage (CT) on greenhouse gases fluxes and soil thermal properties in a corn and soybean field at Lincoln University’s Freeman Farm. The soil of the experimental site was a Waldron silty clay.  Twenty-four  plots were subjected to no-till and 24 additional plots were conventionally tilled in a 10 acres field. Soil air samples were collected from August to November 2011 from static and vented chambers and analyzed for CO₂, CH₄ and N₂O concentrations using a gas chromatograph. Soil temperature (T), thermal conductivity (K), resisitivity (R), thermal diffusivity (D) and volumetric heat capacity (C) were measured using a KD-probe.  Results showed that tillage had a significant effect on CO₂ flux in August and November with NT plots emitting more CO₂ (357.21 and 202.28 mg C-CO₂ m² h^-1 respectively) as compared to CT (277.65 and 144.72 mg C-CO₂ m² h^-1 respectively). Methane  and N₂O  were significantly affected by tillage when NT plots produced higher CH₄ flux  and CT produced higher N₂O flux. Soil R was consistently higher in CT plots while soil C  was consistently higher in NT plots. Soil T and D varied between tillage treatments and sampling dates. The results suggest that tillage affects soil thermal properties which in turn are controlling factors for gases fluxes.