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

Laboratory incubations were conducted to investigate nitrous oxide (N(2)O) 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 (C(2)H(2)) inhibitory technique at 25 degrees C. The production of N(2)O and CO(2) 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 N(2)O 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 N(2)O and CO(2), whereas the addition of NO(3)(-)-N decreased N(2)O production. Compared with the incubation without C(2)H(2), the presence of C(2)H(2) increased NH(4)(+)-N content, but decreased NO(3)(-)-N content, and there was no significant difference in N(2)O production. These results indicate that heterotrophic nitrification contributes to N(2)O production in the soil.