Nitrous oxide emission and reduction in a laboratory-incubated paddy soil response to pretreatment of water regime

A laboratory incubation experiment was conducted to investigate nitrous oxide (N2O) emission and reduction in a paddy soil (Stagnic Anthrosol) response to the pretreatment of water regime. The paddy soil was maintained under either air-dried (sample D) or submerged (sample F) conditions for 110 d before the soil was adjusted into soil moisture of 20% , 40% , 60% , 80% and 100% water holding capacity (WH(-2)) respectively, and then incubated with or without 10% (v/v) acetylene for 138 h at 25 degrees C. At lower soil water content (< or = 60% WHC), N2O emission from the sample F was 2.29 times higher than that from the sample D (P < 0.01). While, N2O emission from the sample F was only 29 and 14 percent of that from the sample D at the soil moisture of 80% and 100% WHC, respectively (P < 0.01). The maximal N2O emissions observed at soil moisture of 80% WHC were about 24 and 186 times higher than the minima obtained at the soil moisture of 20% WHC for the sample F and D, respectively. But at the soil moisture of 80% and 100% WHC, N2O emission from the sample F with acetylene (F + ACE) was comparable to that of the sample D with acetylene (D + ACE). The results showed that the F sample produced N2O ability in denitrification was similar to the sample D, however, the sample F was in the better reduction of N2O to N, than the sample D even after the soil moisture was adjusted into the same level of 80% or 100% WHC. Therefore, the pretreatment of water regime influenced the strength and product composition of denitrification and N2O emission from the paddy soil.