Plummeting global warming potential by chemicals interventions in irrigated rice: A lab to field assessment

Abstract

Methane (CH4) emissions are responsible for the higher global warming potential of rice cultivation. There are scattered reports on the use of chemical interventions for reducing CH4 emissions from rice. A laboratory study was carried out to estimate the CH4 mitigation potential of oxygen releasing chemicals such as magnesium peroxide (MgO2) and calcium peroxide (CaCO2), chelating agent ethylene diamine tetra acetic acid (EDTA), nitrification inhibitors thiourea and neem oil, limus (urease inhibitors), phosphogypsum (PG) a byproduct of phosphate fertilizer industry and ammonium sulfate (AS). The cumulative CH4 emission from soil reduced by 2.0–32.3% under the different treatments during the 45 days’ incubation study. Subsequently, four chemicals having the highest CH4 reduction potential i.e. PG, EDTA, AS, and MgO2 were further evaluated for the mitigation of CH4 and their concurrent impact on nitrous oxide (N2O) emission in a two-year experiment growing rice. PG, EDTA, AS, and MgO2 significantly (p = 0.0025) decreased CH4 emissions by 9.3−27.5% as compared to the control. The cumulative N2O emission were significantly lower by 13.9% under PG as compared to control. The global warming potential decreased by 6.8% with MgO2 to 23.6% with PG. The grain yield increased by 3.1–11.2% under the different treatments. The greenhouse gas intensity (GHGI) was the highest in control (0.309 kg CO2 eq. kg-1 grain yield) and lowest in PG (0.212 kg CO2 eq. kg-1 grain yield). The findings suggest that PG, EDTA, AS, and MgO2 can be used to plummet the global warming potential of irrigated rice soils without any yield penalty. More research is required to be undertaken to evaluate the impact of these chemicals from the perspective of food security in the farmers’ fields.