Effect of Gypsum and Crop Residues on Greenhouse Gas Fluxes from Two Ohio Soils.

Agricultural practices contribute to emissions of the greenhouse gases CO₂, CH₄ and N₂O. The effects of gypsum and crop residues on fluxes of greenhouse gases from soil are not fully understood. A greenhouse experiment was conducted in Ohio to measure gas fluxes from Wooster silt loam and Hoytville clay loam soils treated with gypsum (cumulative of 26.9 Mg/ha applied in four equal doses of 6.72 Mg/ha each) and crop residues (13.4 Mg/ha, applied in one dose). Fluxes of the greenhouse gases CO₂, N₂O and CH₄ were measured bi-weekly. Emissions of CO₂ and N₂O were significantly (P < 0.10) less from Wooster soil as compared to Hoytville soil. A significant reduction was observed (P < 0.10) on the emissions of CO₂ and CH₄ with the addition of gypsum plus residues as compared to their alone application. However, the emission of N₂O was not significantly impacted by the combined application of crop residues and gypsum. A significant interaction effect of residues and Wooster soil was also observed on emissions of CO₂ and N₂O (P < 0.10). However, emissions of CO₂ and N₂O from soils were not significantly impacted by gypsum or residue applied alone for this same soil. A significant reduction in the emissions of cumulative CO₂ and N₂O from Wooster soil was observed with the addition of residue. Cumulative emissions of greenhouse gases were less with the application of gypsum along with residue for the Wooster soil. A reduction in CH₄ emissions by gypsum plus residue for Wooster soils may be due to improved soil aeration and soil was often a sink for CH_4. Gypsum applied with residues reduced CO₂ emissions, suggesting more efficient soil organic matter sequestration with this treatment combination. We conclude that application of gypsum and plant residues affect the emissions of greenhouse gases differently in different soils.