Abstract:

【Objective】 CH4 emission during paddy season under different soil tillages in a rice-wheat double cropping system were investigated for providing scientific instructions to develop rational measures of reducing greenhouse gas emission in the lower reaches of the Yangtze River. 【Method】 A split plot experiment was conducted to study the effects of soil tillage before wheat sowing and soil tillage before rice transplanting on CH4 emission during paddy season by using the method of static chamber-gas chromatographic techniques. Soil tillage before wheat sowing was designed as no tillage before wheat sowing (NTW), rotary tillage before wheat sowing (RTW) and plow tillage before wheat sowing (PTW). Soil tillage before rice transplanting was designed as rotary tillage before rice transplanting (RTR) and plow tillage before rice transplanting (PTR) for each soil tillage before wheat sowing just before rice transplanting. 【Result】 The seasonal variation characteristics of CH4 emission under different soil tillages in a rice-wheat double cropping system were defined, and represented an increasing at the beginning and declining later on. CH4 accumulative emissions from transplanting stage to critical stage of productive tillering accounted for 64.73%-86.84% of the total emission during paddy season. Under NTW, average CH4 emission during paddy season was 53% and 24% higher than under RTW and PTW, respectively, and they were significantly different. Average CH4 emission during paddy season under PTR was significantly higher than under RTR. Total CH4 emissions and total CH4 emissions per unit area yield under different soil tillage followed the same order: NTW+PTR＞NTW+RTR＞PTW+PTR＞PTW+RTR＞RTW+PTR＞RTW+RTR. Correlation analysis showed that CH4 emission flux under different soil tillages was negatively related to soil Eh during paddy season, and a significantly positive correlation between total CH4 emissions and soil organic matter content at 0-5 cm soil layer was also found.【Conclusion】 Total CH4 emissions during paddy season were significantly influenced by soil tillage before wheat sowing and soil tillage before rice transplanting. Annual rotary tillage is one of the effective measures to reduce total CH4 emissions during paddy season from rice-wheat double cropping system in the lower reaches of the Yangtze River.

Key words: rice-wheat double cropping, soil tillage, CH4 emission