稻麦两熟制农田不同土壤耕作方式对稻季CH_4排放的影响

【目的】研究稻麦两熟制农田不同土壤耕作方式对水稻生长季CH4排放的影响,为长江下游稻麦两熟制农田温室气体减排提供对策。【方法】采用裂区设计,利用静态暗箱-气相色谱法研究麦季土壤耕作方式(免耕、旋耕和翻耕)和稻季土壤耕作方式(旋耕和翻耕)对水稻生长季CH4排放的影响。【结果】稻麦两熟制农田不同土壤耕作方式下水稻生长季CH4排放呈先升高后降低的变化趋势,移栽至有效分蘖临界叶龄期CH4累积排放量占全生育期排放总量的比例为64.73%—86.84%。水稻生长季CH4排放总量麦季免耕极显著高于麦季旋耕和麦季翻耕,平均增加53%和24%;稻季翻耕较稻季旋耕平均增加CH4排放量10%,差异达显著水平。不同土壤耕作处理稻季CH4排放总量为:麦季免耕+稻季翻耕麦季免耕+稻季旋耕麦季翻耕+稻季翻耕麦季翻耕+稻季旋耕麦季旋耕+稻季翻耕麦季旋耕+稻季旋耕,"单位产量的CH4排放量"表现趋势相同。水稻生长期内CH4排放通量的季节变化和土壤Eh呈极显著负相关,CH4排放总量与0—5cm耕层土壤有机质含量呈极显著正相关。【结论】麦季土壤耕作方式和稻季土壤耕作方式对水稻生长季CH4排放总量有显著或极显著影响,在长江下游稻麦两熟制农田采用周年旋耕措施能有效减少水稻生长季CH4的排放。

Effects of Soil Tillage on CH4 Emission During Paddy Season in a Rice-Wheat Double Cropping System

【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.