Straw incorporation influences soil organic carbon sequestration, greenhouse gas emission, and crop yields in a Chinese rice (Oryza sativa L.) –wheat (Triticum aestivum L.) cropping system
Crop straw management plays important roles in sustainable agriculture and environmental protection. Straw incorporation has multiple influences on soil organic carbon (SOC) sequestration, greenhouse gas (GHG) emissions, and crop yields, but these influences have rarely been studied simultaneously in a single cropping system. This study was conducted to examine the influence of long-term straw incorporation on the SOC sequestration rate, methane (CH4) and nitrous oxide (N2O) emissions and crop yields in a Chinese rice (Oryza sativa L.) –wheat (Triticum aestivum L.) cropping system in Hydragric Anthrosols under a subtropical monsoon climate. Four straw incorporation treatments were applied: wheat straw incorporation only (WS), rice straw incorporation only (RS), both wheat and rice straw incorporation (WSRS), and no straw incorporation (as a control). The SOC sequestration rate was estimated from the changes in SOC stock in the topsoil (0–20 cm) from 2007 to 2016. The emissions of CH4 and N2O were measured every 7 d when possible using a static chamber method from the 2013 rice season to the 2016 wheat season. Our results showed that the straw incorporation treatments significantly influenced the seasonal CH4 and N2O emissions and rice yield but had no influence on wheat yield. Straw incorporation significantly increased the annual topsoil SOC sequestration rate by 0.24–0.43 t C ha−1 yr−1 and the annual CH4 and N2O emissions by 44–138 kg CH4-C ha−1 yr−1 and 0.68–1.49 kg N2O-N ha−1 yr−1, respectively. Relative to the RS treatment, the WS and WSRS treatments significantly increased annual CH4 emissions by 38% and 61%, respectively. Relative to the RS treatment, the WSRS treatment significantly increased the annual N2O emissions, by 35%. The average annual yields were significantly higher in the WSRS (16.8 t ha−1 yr−1) and RS (16.7 t ha−1 yr−1) treatments than in the WS (15.7 t ha−1 yr−1) and control (15.2 t ha−1 yr−1) treatments. Across the three rotation cycles, the annual net global warming potential and greenhouse gas intensity were similar between the control and RS treatments but were significantly lower in these treatments than in the WSRS and WS treatments. These findings suggest that the RS treatment can simultaneously increase crop yields and environmental sustainability in rice–wheat cropping systems.