Effects of different organic carbon substrates on denitrification and N2O reduction potential in paddy soils
The study investigated effects of organic carbon substrates on denitrification rate and N2O reduction potential in paddy soils,providing scientific evidence for exploring mechanism of the reduction of greenhouse gas emission in paddy fields.Two typical paddy soils[Yangzhou(YZ)and Xinyang(XY)]were selected in this study to investigate denitrification rate and N2O reduction rate using acetylene inhibition method under the addition of three exogenous organic carbons:glucose,formic acid,and methane.Subsequently,anaerobic cultivation experiment was conducted to study the N2O reduction potential of the two paddy soils and to analyze quantitative characteristics of functional genes of nosZ.The results showed that the denitrification rates and the N2O reduction rates of the YZ soil were 9.81-15.25µg·g-1·d-1 and 7.83-12.77µg·g-1·d-1,respectively.These were significantly lower than those of the XY soil under addition of three organic carbon substrates,which might be related to the lower pH value and higher NO-3 content of the YZ soil.Compared with CK treatment,the denitrification rate and N2O reduction rate of the YZ soil under addition of glucose increased by 54.6% and 59.7%,respectively,while the denitrification rate and N2O reduction rate of the XY soil under addition of formic acid increased by 49.9% and 54.4%,respectively.The denitrification rate and N2O reduction rate of the XY soil under addition of methane were significantly higher than those of CK treatment,indicating that methane might act as an electron donor driving N2O reduction.Correlation analysis found that under different addition of carbon source substrates,the N2O reduction potential of the YZ soil was significantly positively correlated to the number of genes nosZⅠ,while these values of the XY soil was significantly positively correlated to the number of genes nosZ Ⅱ.In summary,regulating the properties of organic carbon substrates is an effective way to reduce the net N2O emission potential of different types of paddy soils.
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