Nitrous oxide emissions from the wheat-growing season in eighteen Chinese paddy soils: an outdoor pot experiment

To identify the key soil parameters influencing N2O emission from the wheat-growing season, an outdoor pot experiment with a total of 18 fertilized Chinese soils planted with wheat was conducted in Nanjing, China during the 2000/2001 wheat-growing season. Average 2 seasonal N2O-N emission for all 18 soils was 6 10 mg m(-2), ranging from 193 to 1,204 mg m(-2), approximately a 6.2-fold difference between the maximum and the minimum. Correlation analysis indicated that the seasonal N2O emission was negatively correlated with soil organic C (r(2)=0.5567, P<0.001), soil total N (r(2)=0.4684, P<0.01) and the C:N ratio (r(2)=0.4530, P<0.01), respectively. A positive dependence of N2O emission on the soil pH (r(2)=0.3525, P<0.01) was also observed. No clear relationships existed between N2O emission and soil texture, soil trace elements of Fe, Cu and Mer, and above-ground biomass of the wheat crop at harvest. A further investigation suggested that the seasonal N2O-N emission (E, mg m(-2)) can be quantitatively explained by E=1005-34.2SOC+4.ISa (R-2=0.7703, n=18, P=0.0000). SOC and S-a represent the soil organic C (g kg(-1)) and available S (mg kg(-1)), respectively.