The contributions of hydroxylamine and nitrite to NO and N2O production in alkaline and acidic vegetable soils

Abstract

The contribution of hydroxylamine (NH2OH) and nitrite (NO2−) to nitric oxide (NO) and nitrous oxide (N2O) production remains unclear in vegetable production soils. Soils collected from six typical greenhouse vegetable fields were incubated for 48 h following amendment with 1 mM NaNO2, 10 μM NH2OH, or 1 mM NaNO2 + 10 μM NH2OH. The importance of abiotic processes on the NO and N2O formation from the NH2OH and NO2− were studied by irradiating the soil samples with γ-irradiation. NO2− amendment significantly stimulated NO production, while the NH2OH-dependent NO production was minimal. NH2OH stimulated more abiotic N2O production in alkaline soils than in acidic soils (p < 0.05), while NO2− stimulated more biotic N2O production in acidic soils than in alkaline soils (p < 0.05). The NH2OH- and NO2−-dependent sources produced biotic or abiotic N2O with site preference (SP) values of 27.4–36.5‰, which is similar to those from ammonia-oxidizing archaea (AOA) or ammonia-oxidizing bacteria (AOB) sources (25.1–34.2‰), indicating that abiotic N2O production were closely linked with biotic NH3 oxidation. The variability of NO2−+NH2OH-induced N2O production can be explained by the soil organic carbon and iron concentrations, whereas NO2−-induced NO production can be explained by the soil pH. NO2− addition dominated NO production in all soils. Furthermore, NO2− addition increased biotic N2O production in acidic soils, while NH2OH addition increased abiotic N2O production in alkaline soils. The presence of NO2− could significantly stimulate the abiotic conversion of NH2OH to N2O in soils with low soil organic carbon and high iron concentrations. Thus, assessing the abundance of NH2OH and NO2− could provide crucial information for understanding NO and N2O production procedures in vegetable soils. • The chemical decomposition of NO2− dominated NO production in all soils. • The NH2OH stimulated abiotic N2O production in alkaline soils. • The NO2− stimulated biotic N2O production in acidic soils. • The SP for abiotic NO2−-/NH2OH-related N2O were in the same range as AOB/AOA sources.