Primings of soil organic matter and denitrification mediate the effects of moisture on nitrous oxide production

Abstract

Abstract Nitrogen-fertilized agricultural soils are major emitters of the potent greenhouse gas nitrous oxide (N2O). Although soil moisture is known to drive N2O production, the influence of moisture on the priming effects of labile N additions, which alter the N2O production from native soil organic matter (SOM), remains understudied. We investigated how moisture impacts N2O primings, nitrification kinetics, and allocation of N2O sources between nitrification and denitrification. We evaluated urea additions at five water-filled pore spaces (WFPS): 31, 41, 53, 65, and 78%. Based on δ15N–N2O site preference (SP), the denitrification source (encompassing bacterial- and nitrifier-denitrification) amply dominated across all moistures. At moistures >60% WFPS, SP exhibited a narrow range of 1.2–1.6‰, whereas at 31% WFPS, SP rose to 9.4‰ (P