[Effects of Irrigation and Biochar Application on the Respiratory Temperature Sensitivity of Paddy Soil]

The ecosystem respiration and temperature sensitivity (Q₁₀) of paddy soil play very important roles in the emission of greenhouse gases from paddy ecosystems. Under intermittent irrigation and flooding irrigation conditions, a static opaque chamber and gas chromatography method were applied to study the regulation and influence of ecosystem respiration and Q₁₀ using five treatments:no fertilizer (CK), conventional fertilization (NPK), 10t·hm^-2 biochar with chemical fertilizer (LBC), 20t·hm^-2 biochar with chemical fertilizer (MBC), and 40t·hm^-2 biochar with chemical fertilizer (HBC). The results showed that:① The temperature sensitivity coefficients (Q₁₀) of ecosystem respiration under flooding irrigation were 4.45 (CK), 7.40 (NPK), 6.44 (LBC), 4.58 (MBC), and 3.87 (HBC), respectively. Flooding irrigation significantly reduced the Q₁₀ value of the paddy field ecosystem compared to intermittent irrigation (P<0.01). CK, NPK, LBC, MBC, and HBC decreased by 48.6%, 55.2%, 67.9%, 70.3%, and 70.8% under flooding irrigation, respectively. ② Whether intermittent irrigation or flooding irrigation was adopted, the application of fertilizer with biochar increased the respiration of the paddy field ecosystem than conventional fertilization treatment, but the effect of different biochar levels on respiration was not significant. ③ The application of chemical fertilizer with medium or low amounts of biochar increased the temperature sensitivity of respiration compared with no fertilization in the paddy field ecosystems (P<0.05), but both MBC and HBC treatments reduced the Q₁₀ value of paddy field ecosystem compared with NPK. Furthermore, the temperature sensitivity of respiration in the paddy field ecosystem decreased with an increase in the level of biochar application. Therefore, under the two irrigation methods, HBC treatment was more effective than LBC and MBC treatments to inhibit the effect of increasing soil temperature on the respiration of the ecosystem.