Remarkable N 2 O emissions by draining fallow paddy soil and close link to the ammonium-oxidizing archaea communities

Fallow paddies experience natural flooding and draining water status due to rainfall and evaporation, which could induce considerable nitrous oxide (N2O) emissions and need to be studied specially. In this study, intact soil columns were collected from a fallow paddy field and the flooding-draining process was simulated in a microcosm experiment. The results showed that both N2O concentrations in the soil and N2O emission rates were negligible during flooding period, which were greatly elevated by draining the fallow paddy soil. The remarkable N2O concentrations in the soil and N2O emission/h during draining both had significant relationships with the Arch-amoA gene (P   0.05). However, the number of AOA and the nitrification substrate (NH4+-N) in the 0–10 cm layer were significantly higher than in the 10–20 cm layer (P < 0.01), indicating N2O production in the 0–10 cm layer might be higher than the measured concentration and would contribute considerably to N2O emissions as shorter distance of gas diffusion to the soil surface.