Yupeng Zhao Qingyong Bian ^* 志多 董 Xiaojuan Rao ^* Zhiguo Wang ^* Yanbo Fu ^* Bolang Chen ^*

• Xinjiang Academy of Agricultural Sciences, Urumqi, China

This study explores the improvement effects of different organic materials on compacted clayey soil in southern Xinjiang, focusing on their impact on soil chemical properties and microorganisms to identify the optimal carbon source input and provide theoretical support for the rational use of organic materials in the region. Through field experiments, five organic materials (farmyard manure, biochar, commercial organic fertilizer, microbial fertilizer, and mineral potassium humate) were applied to evaluate their effects on the physical and chemical properties of clayey soil, as well as on cotton agronomic traits and yield. Results showed: (1) All organic materials improved soil structure, with farmyard manure significantly reducing soil bulk density and salinity, while increasing soil organic matter, total nitrogen, and available nutrients, thus promoting cotton height, stem thickness, and yield, with the optimal application rate being 36,000 kg/hm²;(2) The application of different organic materials enhanced the organic matter, total nitrogen, hydrolyzable nitrogen, available phosphorus, and rapid available potassium contents in the 0-40 cm soil layer, while increasing the populations of bacteria, fungi, and actinomycetes, and reducing soil salinity; (3) We used structural equation model (SEM) to comprehensively explore the mechanism of organic matter input on soil microbial quantity, soil physicochemical properties and cotton yield. The mechanism further confirmed by the model is as follows: organic matter input mainly regulates microbial quantity and microbial species richness, thereby improving soil physicochemical properties and thereby increasing cotton yield.The addition of all five organic materials contributed to improved cotton growth and yield, with a comprehensive evaluation indicating that farmyard manure at 150% of the recommended rate had the best improvement effect. In conclusion, farmyard manure serves as an effective soil amendment that not only alleviates soil compaction but also significantly enhances cotton growth potential, aligning with the goals of sustainable agricultural development.