The Effects of Sand-Fixing Agents and Trichoderma longibrachiatum on Soil Quality and Alfalfa Growth in Wind-Sand Soil

The degradation of sandy land in Inner Mongolia presents a substantial threat to regional ecological security and the sustainable development of agriculture and animal husbandry. Planting alfalfa serves as a crucial recovery strategy; however, the inadequate capacity to retain water and nutrients impedes this process. The current reliance on a singular microbial remediation method has demonstrated limited effectiveness in addressing the challenges posed by sandy soil. While traditional sand-fixing agents can improve soil nutrients, they lack biological activity. Furthermore, the synergistic mechanisms between these approaches and their ecological impacts within a single season remain poorly understood. This study involved a pot experiment utilizing wind-sand soil as the substrate to evaluate the soil physicochemical properties, enzyme activities, and microbial community structure associated with the stress resistance of alfalfa. The results indicated that the medium concentration of sand-fixing agent (1:75) exhibited optimal water retention performance, thereby creating a conducive growth microenvironment for Trichoderma longibrachiatum and mitigating fluctuations in surface temperature and humidity. The combined treatment significantly improved the alpha diversity of soil microorganisms, thereby improving the stability and stress resistance of the system. Through the synergistic approach of “sand fixation and water retention–nutrient activation–improved stress resistance”, the microenvironment of sandy land was effectively improved, promoting alfalfa growth. This method offers “environmentally friendly and synergistic” technical support for the efficient cultivation and ecological restoration of alfalfa in sandy regions, while also contributing to the high-quality development of grassland animal husbandry.