Effect of straw returning on soil organic carbon in rice-wheat rotation system: A review

The rice-wheat rotation model of crop planting is widely used globally, and worldwide, straw returning is the main method of crop straw treatment. However, the straw return method commonly used in the modern rice-wheat rotation system has many adverse effects on the levels and improvement of soil fertility and crop yield, and there is no systematic theory of rice and wheat straw returning to use as a guide. In this paper, we concluded that: in the rice-wheat rotation system, returning 1,500-4,500 kg/ha of rice straw and 2,250-6,750 kg/ha of wheat straw to the field helps increase the organic carbon content and quality of the soil and promotes high annual yields; conventional mixing of straw into the field can increase the organic carbon content of the soil in a short time; long-term use of concentrated ditch-buried straw return has obvious advantages over other straw returning methods in increasing the accumulation of soil organic carbon; the combination of little or no tillage plus straw returning helps increase the content and quality of organic carbon in soil; and when the soil water content is 15%-22.5%, it is the most conducive to the accumulation of soil organic carbon. In addition, we also provide relevant suggestions for future research directions on straw returning via systematic analyses and thought processes.