Nitrite behavior accounts for the nitrous oxide peaks following fertilization in a fluvo-aquic soil

Abstract

It has been widely demonstrated—both in the field and the laboratory—that N fertilization stimulates peaks in nitrous oxide (N2O) emissions in agricultural soils. However, the mechanisms responsible for this phenomenon remain unclear. In this study, three aerobic incubation experiments were designed to: (1) evaluate the effects of urea and nitrification inhibitors (NIs) on inorganic N concentrations and N2O emissions; (2) establish the relationship between nitrite concentration and N2O emission by adding different amounts of nitrite to soil, and identify the contributions of abiotic processes to N2O production from nitrite by sterilization; and (3) explore the underlying reasons for nitrite accumulation by using 15N tracer methods. Compared with NI treatments, substantial nitrite accumulated in the UREA treatment, mainly attributed to the inhibitory effects of high ammonium from urea hydrolysis on transformation of 15N-nitrite to 15N-nitrate. N2O emission from soil was related to soil nitrite concentration, according to the Michaelis–Menten relationship (R 2 = 0.998; P < 0.01). No significant N2O emission was observed in sterilized soil, indicating that N2O production was a microbial process with the probable dominance of nitrifier denitrification (ND). In conclusion, our results suggest that ammonium fertilizer stimulates nitrite accumulation by inhibiting nitrite transformation to nitrate, thus resulting in an increase in N2O emissions, while NIs reduce N2O emissions by suppressing nitrite formation.