This study was conducted in an alfalfa field at the Luhuatai experimental site of the Institute of Plant Protection， Ningxia Academy of Agriculture and Forestry Sciences， where Beauveria bassiana and Metarhizium anisopliae were applied in alternate rows for three consecutive years. The results showed that both entomopathogenic fungi provided effective control of Odontothrips loti， with average control efficacies of 34.8% and 30.3%， respectively. Compared with the control， three years of B. bassiana application significantly improved soil physicochemical properties， with available phosphorus and soil organic carbon increasing by 67.2% and 41.7%， respectively， showing greater improvement than M. anisopliae. Soil enzyme activities were also enhanced， with increases of 36.91% in sucrase， 64.20% in alkaline phosphatase， and 31.03% in catalase. Application of M. anisopliae increased sucrase activity by 30.32% and catalase activity by 24.42% relative to the control. Compared with the soil bacterial community， soil fungal community structure was more strongly altered by the two biocontrol fungal treatments. Meanwhile， the relative abundance of beneficial taxa such as Sphingomonas increased， whereas the proportion of pathogenic fungi such as Fusarium declined. Overall， this study provides a theoretical basis and practical reference for pest biological control and the sustainable development of grassland agriculture in the Ningxia region.

Alfalfa pests  /  Biological translation  /  Soil physical and chemical properties  /  Rhizosphere microecology