Urea- and nitrapyrin-affected N2O emission is coupled mainly with ammonia oxidizing bacteria growth in microcosms of three typical Chinese arable soils

It is unclear how inhibition of nitrous oxide (N2O) emissions by nitrification inhibitor (NI) is regulated through the ammonia oxidizing bacteria (AOB) or archaea (AOA) in arable soils. In this study, we investigated effects of 2-chloro-6-(trichloromethyl)-pyridine (Nitrapyrin, NP) on N2O emissions, and characterized the ammonia oxidizing microbial community in three arable soils typical of northern China. In alluvial, black, and paddy soils, average N2O emission rates were increased by addition of urea by 3.5, 0.7 and 2.1 pM N2O g−1 soil h−1, respectively, but were reduced by 2.9, 0.4 and 2.2 pM N2O g−1 soil h−1 when urea was applied with NP. The stimulation and suppression of N2O emission by urea and NP occurred alongside fluctuation in the growth of AOB in alluvial and paddy soils (P < 0.01). Weak stimulation and suppression of N2O emissions by urea and NP corresponded with weak effects on AOB abundances in the black soil. Changes in N2O emissions were not significantly correlated with AOA abundances in any of the three soils. The results showed that differential responses of N2O emission to urea and NP application in arable soils can be mainly explained by differences in growth of ammonia oxidizing bacteria.