A Study of Paddy CO2 Emissions under Long-Term Fertilizations and Associated Impact Factors

A field experiment was made using static chamber-GC theory to observe CO₂ emissions from rice paddy that have been fertilized for 25 consecutive years. Impact factors derived from the experiment were also studied. Seasonal variations of CO₂ flux presented a similar pattern, though they were different in treatment. CO₂ flux peaks appeared in the flooding season, with the bottom in the drainage. Seasonal trends of CO₂ flux went along with the air temperature near the ground. Chemical fertilizer applications produced more CO₂ flux, compared with other treatments, though there was no significant correlation between other treatments and the treatment with only chemical fertilizer. NPKS had the largest CO₂ flux, or 502.58 mgldrm^-2h^-1, and CK the lowest flux, or 249.16 mgldrm^-2h^-1 . There was a significant negative correlation between CO₂ flux and water depth (p<0.01). Water is a most important factor that controls paddy CO₂ flux. Temperature is another most important factor that controls CO₂ flux from rice-involved plots, in a range of 13.33degC~38.59degC. There is a significant exponential relationship between CO₂ flux and temperature, or F=20.1365e ^0.088838T (p<0.01). Temperature coefficient (Q10) was 2.43. Both soil pH and Eh values were correlated with CO₂ flux (p<0.01), though further study is needed to clarify the mechanism.