Long-Term Increases in Continuous Cotton Yield and Soil Fertility following the Application of Cotton Straw and Organic Manure

Long-term continuous cotton cropping results in a significant decrease in soil quality and soil organic carbon, threatening cotton yield. The application of organic amendments is considered an effective management practice for the sustainability of soil productivity and often increases yield. However, the sustainable improvement in the cotton yield, stability, and soil fertility over time resulting from organic amendments with cotton straw and organic manure still need to be confirmed with research, especially under a continuous cotton cropping system. This study evaluated the effect of 12 years of consecutive application of cotton straw and organic manure on continuous cotton yield, soil quality, and soil organic carbon. Four treatments, i.e., chemical N and P fertilizers (NP, control), NP plus cotton straw (NPS), NP plus manure (NPM), and NP plus cotton straw and manure (NPSM), were carried out. The results indicated that the addition of cotton straw and organic manure improved the temporal stability and sustainability of cotton yield. The combination of cotton straw and organic manure resulted in the greatest improvement, increasing the average annual cotton yield by 32.28% compared with the control (NP). A correlation analysis revealed that cotton yield was closely related to soil quality and soil organic carbon. The application of cotton straw and organic manure increased cotton yield by enhancing soil fertility, especially the quantity and quality of soil organic carbon, which improved the supply and cycling of soil nutrients and benefited the stability and sustainability of the cotton yield. Reusing cotton straw and organic manure could improve the sustainable productivity of cotton soil and provide additional environmental value as well as having great potential for cleaner and sustainable cotton production.