[Evaluation of Annual Straw Return Based on Soil Carbon Pool and Crop Yield in Wheat-maize Cropping System]

The treatment and recycling of crop straws has become a hot spot in the field of agricultural research, with the need to optimize the management of wheat-maize annual straws, improve the carbon efficiency of cropping systems, and promote the sustainable production of wheat-maize annual straw. Based on an 8-year long-term field trial, two treatments, wheat-maize double cropping （WS-MS） and wheat-maize single cropping （WS-MN）, were set up, and the effects of straw returning on soil organic carbon （TOC） content, oxidizable organic carbon （EOOC） content, soil carbon storage, carbon pool management index （CPMI）, carbon use efficiency, and crop yield were compared between WS-MS and WS-MN treatments. The results showed that the content of TOC in WS-MS and WS-MN increased by 8.1% and 5.5%, respectively, and the content of EOOC in WS-MS and WS-MN increased by 50.4% and 45.5%, respectively. The WS-MS and WS-MN treatments increased organic carbon storage by 20.5% and 18.3%, respectively, but the WS-MS treatment did not significantly increase organic carbon storage compared with that in the WS-MN treatment. The carbon pool index （CPI）, carbon pool activity （CPA）, carbon pool activity index （CPAI）, and CPMI of WS-MS were 3.7%, 20.5%, 2.2%, and 7.9% higher than those of WS-MN, respectively. The annual yield of WS-MN was 0.2% higher than that of WS-MS. The annual production efficiency and ecological efficiency of WS-MN were 136.1% and 64.2% higher than those of WS-MS, respectively. The carbon benefit of the WS-MN treatment was significantly higher than that of the WS-MS treatment. Therefore, considering the straw return method, straw carbon utilization efficiency, and crop yield, the single season return of wheat straw is more suitable for the efficient utilization of annual straw resources in the intensive wheat-maize double cropping system in the Huang-Huai-Hai Region, without significantly affecting the annual grain yield of wheat-miaze and its soil carbon pool.