Straw Return or No Tillage? Comprehensive Meta-Analysis Based on Soil Organic Carbon Contents, Carbon Emissions, and Crop Yields in China

Conservation tillage methods, including straw return (SR) and no tillage (NT), are widely used to improve the soil organic carbon (SOC) content and crop yield. However, applying SR or NT separately has become a common practice for farmers producing different crops or those in different regions. Evaluating the effects of SR or NT on the SOC content, carbon emissions, and crop yield are important for guiding the correct application of conservation tillage and promoting sustainable agricultural development. Therefore, we conducted a meta-analysis based on 1014 sets of data obtained in China to assess the effects of SR and NT on the SOC content, carbon emissions, and crop yield. Compared with no straw return, SR increased the SOC content and crop yield by 10% and 8.6%, respectively, but with no significant impact on carbon emissions. Compared with conventional tillage, NT increased the SOC content by 2.9% and reduced the carbon emissions and crop yield by 18% and 3.9%, respectively. We also found that SR combined with NT had an additive effect, where the combination improved SOC more than applying SR or NT alone. If applying SR or NT alone, the specific climatic conditions, soil characteristics, and field management strategies need to be considered to maximize SOC. In particular, SR should be used in limited hydrothermal conditions (low temperature or low precipitation) and areas where rice-wheat rotation is implemented. NT can be used under any climate conditions, but it can effectively increase the SOC content in continuous wheat cropping areas.