Rice Yield and Greenhouse Gas Emissions Affected by Chinese Milk Vetch and Rice Straw Retention with Reduced Nitrogen Fertilization

Straw retention and fertilization management can affect rice yield and greenhouse gas (GHG) emission in paddy field. To investigate the effect of leguminous green manure and straw retention plus nitrogen (N) fertilizer on rice yield and GHG emissions, field experiments were conducted from 2017 to 2018 and four treatments were designed, including the treatments of Chinese milk vetch (Astragalus sinicus L.) and rice (Oryza sativa L.) straw retention with reduced chemical N fertilizer application amount named RA (6000 kg hm(-2) rice straw plus 102 kg hm(-2) N fertilizer during early and late rice respectively), RB (6000 kg hm(-2) rice straw plus 87 kg hm(-2) N fertilizer during early and late rice season respectively), RC (6000 kg hm(-2) rice straw plus 72 kg hm(-2) N fertilizer during early and late rice season respectively) and control CK (winter fallow, without straw retention, 120 kg hm(-2) N fertilizer during early and late rice season respectively). The results showed treatments RA, RB, and RC significantly increased the early rice yield by 15.79, 21.27, and 13.60% (P < 0.05), and RA and RB significantly increased the annual yield by 14.76 and 15.79% (P < 0.05) compared with control CK. For CH4 cumulative emissions, only RB had no significant impact on it (P > 0.05); treatments RA, RB, and RC had no significant effect on N2O cumulative emissions (P > 0.05). Meanwhile, treatments RA and RC significantly increased GWP and green-house gas emission intensity (GHGI) (P < 0.05) of CH and N2O, but the difference between RB and control CK was not significant (P > 0.05). Therefore treatment RB had the best effect on rice production and GHG mitigation in paddy fields.