Research Progress on the Effect of Straw Returning on Soil Greenhouse Gas Emissions

Straw return is an effective method for enhancing soil fertility through resource utilization. As straw itself is rich in carbon, nitrogen, phosphorus, potassium, and other elements, its incorporation into the soil can significantly improve soil physicochemical properties, thereby promoting soil nutrient cycling and achieving the goals of fertilization and soil improvement. However, the impact of straw return on greenhouse gas (GHG) emissions—primarily carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O)—from agricultural soils is highly complex. Most field-based observational studies indicated that straw return tends to increase the emission of specific GHGs, particularly CH₄ from paddy fields or N₂O under certain conditions, although this effect was modulated by climatic conditions and regional differences. Importantly, the responses of these three gases often differ; some studies had shown that under specific environmental conditions, straw return could suppress the emission of N₂O and CH₄. Furthermore, results from short-term experiments often differed from those of long-term experiments (exceeding five years). Long-term straw return might lead to a soil priming effect or carbon saturation, potentially resulting in an increased global warming potential (GWP). Through a literature review, this paper systematically elucidated the primary mechanisms by which straw return affected GHG emissions, starting from the soil processes involved in GHG production, and summarized the influencing factors. The study found that the patterns of straw return, temperature, and soil properties were three critical factors significantly influencing GHG emissions. Additionally, this research explored various measures to achieve GHG emission reduction, such as the application of straw-derived biochar, water-saving irrigation, optimized fertilizer management, and the integration of cropping and livestock systems. Future research directions were also discussed, including further investigation into key factors causing GHG emissions outside the farmland system (e.g., fertilizer and pesticide production, agricultural product processing and transportation, agricultural machinery use), in-depth analysis of the mechanisms underlying effective mitigation measures, and the influence of soil environmental factors on GHG emissions. This systematic reviewed aims to provide a theoretical basis and practical reference for promoting the efficient utilization of straw and achieving GHG emission reduction in agricultural systems.