Regional Variations in Nitrous Oxide in the Indian Groundwater: Influence of Agricultural Practices, Irrigation, and Rainfall Patterns

Abstract

Intensified agricultural practices, particularly the increased use of nitrogen fertilizers, are fueling the rise of nitrous oxide (N2O) in groundwater. This gas is produced through the nitrification/denitrification of inorganic nitrogen in the groundwater. Based on combined chemical and isotopic analyses of nitrate (NO3-) and chemical analysis of N2O, we present the first-ever evidence for widespread denitrification-driven N2O accumulation in Indian groundwater that often exceeds 25 times the saturation level. This phenomenon is particularly concerning in regions where low precipitation is received with intensive groundwater irrigation, leading to an inadvertent accumulation of N2O in the groundwater. The emission factor for groundwater (EF5g) from the agricultural soils of India is significantly lower (0.00067) than the global mean values (0.008), suggesting that indirect fluxes of N2O from the Indian soils are lower than the global mean. Implementing sustainable agricultural practices and maximum feasible control measures could further reduce indirect N2O emissions from agricultural soils and their associated environmental consequences.