Effects Of Straw Return On Soil Organic Carbon And Greenhouse Gas Emission

As a large agricultural country,China has abundant straw resources.Straw renturn is one of resource recycling and cost-effective managements.The returning straw can decompose into the soil carbon pool to increase the soil organic carbon content,but it also increase the greenhouse gas emissions such as nitrous oxide and methane.Thus,discussing the input response relationship between straw return and soil organic carbon and agricultural greenhouse gas emissions,exploring the feasibility of improving soil carbon sequestration and controlling the greenhouse gas emissions through optimization of straw return mode are critical to optimize the eco-environmental benefits of the farmland and realize low-carbon and green agricultural development.In this paper,the impact mechanism of straw return on soil organic carbon and agricultural greenhouse gas emissions in southern agricultural areas was taken as the research object.A Meta-analysis method was used to quantitatively assess the effects of straw return on soil organic carbon and greenhouse gas emissions,and the characteristics of soil organic carbon and greenhouse gas emissions under different straw return modes were simulated by DAYCENT to optimize farmland management measures for straw return.The main findings were as follows:Meta analysis showed that:?1?Straw return significantly increased the SOC content,and the SOC sequestration was affected by the application of nitrogen fertilizer and the duration of straw return.Increasing the nitrogen fertilizer input and prolonging the period of straw return could benefit the effects of SOC sequestration.?2?The impact of straw return on CH₄ emissions was mainly limited by the choice of water management methods.The effect size of methane emission response to straw return was the least under the moister irrigation.?3?Generally,straw return has no significant effect on N₂ O emissions.Results indicated continuous flooding and reducing nitrogen fertilizer input can significantly reduce N₂ O emissions under straw return.The results of different straw return modes showed that:?1?Compared to no straw return treatment,SOC content was observed significantly increased by 5.6% to 10.58% under straw return in different modes.Straw half-returning could basically maintain the existing level of soil organic carbon content,and it was more conducive to soil organic carbon accumulation when it combined with nitrogen-reduced fertilization and continuous flooding.?2?A significant increase by 8.90% to 26.24% of CH₄ emissions was observed under different straw return modes.The results present herein indicated straw return combined with moister irrigation and nitrogen-reduced fertilization contributed the least to CH₄ emission increase.?3?N₂O emission increased by 13.09% to 39.34% in different straw return modes.Straw return combined with conventional nitrogen application and continuous flooding showed the maximum offset effect on N₂ O emission increase that caused by straw return.?4?The simulation results showed that half-amount straw return combined with conventional nitrogen application and moister irrigation had the best effects on SOC sequestration and emsission mitigation when considering the effect of straw return on agricultural greenhouse gas emissions only.