[Statistical analysis of factors influencing N2O emission from paddy fields in Asia]

Most previous studies attributed variation in N2O emission from paddy fields to water managements and fertilizer input. In this study, we compiled a database of N2O emission from paddy fields in Asia, including water management, type and amount of nitrogen fertilizer, soil property, climate and rice types. After screening the influencing factors with statistical significance (p < 0.01) such as different water managements, N input, different organic N types, interaction of soil total nitrogen content and different pH levels, different annual temperature levels, and different rice types, a linear model was established to link N2O emission to those factors, which could totally explain up to 60.7% of the observed variation in N2O emission. The most important influencing factor was the amount of N fertilizer input, which had significantly positive correlation with N2O fluxes. Relative emission fluxes of continuous flooding, intermittent irrigation and wet irrigation were 0.17:0.56: 1. The soil total nitrogen content had significantly positive effect on N2O fluxes while the optimum pH for N2O emission was pH > 8. Straw of N-fixing crop had much higher fluxes than other organic fertilizers while manure had no significant effects on increasing N2O emission. Application of other crop straws actually reduced N2O emission by 36%, as compared with fields without organic N input. The relative fluxes for early rice and later rice were 71% and 48% of that for single rice, respectively. Inclusion of more influencing factors such as soil property, climate and rice type helped explaining more of the variations in the observed N2O emission from paddy fields.