Can Potassium Chloride Mitigate N2O Emissions from Grassland Soil?

Nitrous oxide (N₂O) is the third most important greenhouse gas with a global warming potential 300 times more than carbon dioxide. The main sources of N₂O in grassland soils are nitrogen fertilizers application and animal excretion. The objective of this research was to test the hypothesis that KCl can inhibit N₂O emissions from soil. The experimental design was completely randomized with 5 treatments and 4 replicates. The treatments were five concentrations of KCl diluted in cattle urine (0.0, 5.0, 10.0, and 20.0 g L^-1). The N₂O emissions from a tropical Ferralsol were evaluated in an incubation under controlled conditions. The N₂O emissions were evaluated using static closed chamber and the gas concentration was determined by gas chromatography. N₂O emissions were integrated over time to calculate the cumulative emissions and the amount of N lost as N₂O, then the ANOVA was performed. To analyze the effect of KCl concentrations on N₂O emission a polynomial orthogonal contrast was tested. The % of applied N emitted as N₂O was 3.22 (±1.21), 4.44 (±0.65), 3.03 (±0.42) and 1.17 (±0.23) for the KCl concentrations of 0.0, 5.0, 10.0 and 20.0 g L^-1 of urine, respectively. The KCl addition to the soil affected N₂O emissions (P < 0.01). The effect of KCl concentration was curvilinear (P < 0.01; R² = 0.87). A possible mechanism that explain the reduction of N₂O production when KCl concentration increases is that higher KCl concentration maybe inhibit the nitrification. The increase in the ions K⁺ probably affect negatively the nitrification. The KCl addition to a grassland soil diminish N₂O emissions and possibly can be used to mitigate N₂O production.