Mitigation options of methane emission and nutrient losses by surface runoff during rice growing season in a rice-wheat double cropping system

Two field experiments were carried out to study the effects of soil tillage modes on methane emission and characteristics of nutrients losses by surface runoff under natural rainfall conditions,respectively,during rice growing season in an intensive rice-wheat double cropping system in the lower reaches of Yangtze River.The results showed that total methane emissions during paddy season were significantly influenced by soil tillage modes,following the order of no tillage before wheat sowing(NTW)+plowing before rice transplanting(PTR) NTW+rotary tillage before rice transplanting(RTR) plowing before wheat sowing(PTW)+PTR rotary tillage before wheat sowing(RTW)+PTR PTW+RTR RTW+RTR.Annual rotary tillage was one of the effective measures to reduce total methane emissions during paddy season in rice-wheat double cropping system.Under conventional fertilization conditions,the total runoff losses of total nitrogen(TN) and total phosphorus(TP) reached 3.92 kg/hm2and 147.30 g/hm2,respectively,and the rates of nutrients losses reached 1.45% and 0.22%,respectively.In contrast with conventional fertilization treatment,wheat straw returning,wheat straw returning plus fertilizer reduction,and nitrogen fertilizer retruding treatments could effectively reduced TN and TP losses by runoff during the whole rice growing season.These results indicate that rational agronomic measures could reduce methane emission and nutrient losses by surface runoff during rice growing season in a rice-wheat double cropping system.