Integrated Organic-Inorganic Nitrogen Fertilization Mitigates Nitrous Oxide Emissions by Regulating Ammonia-Oxidizing Bacteria in Purple Caitai Fields.

Purpose Nitrogen (N) fertilizer application in agricultural soil is a primary anthropogenic nitrous oxide (N₂O) source. Currently, the effect of the N fertilizer type on N₂O emissions from upland soil has been rarely reported. To this end, impacts of various types of N fertilizer on N₂O emissions in purple caitai (Brassica campestris L. ssp. chinensis var. purpurea) fields are investigated in this work. The field experiment was carried out with four treatments, including inorganic N fertilization (I), organic N fertilization (O), integrated organic-inorganic N fertilization (I+O) and no fertilization (CK). The nitrifier/denitrifier abundance was determined using absolute real-time quantitative PCR. Compared with I and O, I+O significantly increased dissolved organic C content, microbial biomass C and microbial biomass N by 24–63%, 12–38% and 13–36% on average, respectively. Moreover, the seasonal cumulative N₂O-N emissions and fertilizer-induced N₂O emission factor under I+O were significantly lower than those under I and O by 17–29% and 23–39%, respectively. The results indicate that N fertilizer type significantly affects the N₂O emissions, and the integrated organic-inorganic N fertilization can mitigate the N₂O emissions primarily by inhibiting the nitrification mediated by ammonia-oxidizing bacteria in purple caitai fields. Integrated organic-inorganic N fertilization is an ideal N fertilization regime to enhance soil fertility and yield and reduce N₂O emissions in the upland fields. [ABSTRACT FROM AUTHOR]