Nitrous oxide production at different soil moisture contents in an arable soil in China

Laboratory incubations were conducted to investigate nitrous oxide (N2O) production from a subtropical arable soil (Typic Plinthodults) incubated at different soil moisture contents (SMC) and with different nitrogen sources using a 10% (v/v) acetylene (C2H2) inhibitory technique at 25°C. The production of N2O and CO2 was monitored during the incubations and changes in the contents of KCl-extractable NO− 3-N and NH+ 4-N were determined. The production of N2O increased slightly with an increase in SMC from 40% water-holding capacity (WHC) to 70% WHC, but increased dramatically at 100% WHC. After incubation the NO− 3-N content increased even at a SMC of 100% WHC. At a SMC of 100% WHC, the addition of NH+ 4-N promoted the production of N2O and CO2, whereas the addition of NO− 3-N decreased N2O production. Compared with the incubation without C2H2, the presence of C2H2 increased NH+ 4-N content, but decreased NO− 3-N content, and there was no significant difference in N2O production. These results indicate that heterotrophic nitrification contributes to N2O production in the soil.