Effects of Returning Straw and Milk Vetch on Rice Growth and Greenhouse Gas Emissions

The effects of different nitrogen application levels on rice yield and greenhouse gas (NO 2 , CH 4 ) emissions from rice fields under the combined action of straw and milk vetch. Two treatments were set up in the main area of this experiment: R 0  (no straw returned to the field, 0); R 1  (amount of straw returned to the field under normal conditions, 6000 kg·hm -2 ). Before turning the straw back into the field, use a circular knife to cut the straw into 10~13 cm.And 3 kinds of nitrogen application treatments in the sub-district: N 1  (no nitrogen application, 0), N 2  (nitrogen application, 15 kg·hm -2 ), N 3  (nitrogen application, 30 kg·hm -2 ), two-factor cross-combination,and a non-nitrogen control CK, total of 7 treatments. The results showed that in 2017, early rice R 1 N 2  treatment increased the most obvious yield, which was 32.44% higher than CK, and late rice R 1 N 1  treatment increased the most significantly, which was 17.91% higher than CK. CH 4  emission is positively correlated with the straw returned to the field. N 2 O is the opposite. The N 2 O emission flux was highest in the treatment of R 1 N 3 , and the CH 4  emission flux was the highest in the treatment of R 1 N 2 .