Synergistic Effects of Nitrogen-Fixing, Phosphate-Mobilizing, and Fungicidal Microbial Consortia in Enriched Vermicompost for Sustainable Agriculture in Semi-Arid Regions

Declining soil fertility, overreliance on mineral fertilizers, and rising phytopathogen pressure threaten sustainable agriculture in semi-arid regions such as Northern Kazakhstan. Traditional composting and vermicomposting improve soil health but often fail to deliver the nutrient efficiency and phytosanitary protection provided by chemical fertilizers. This study evaluates a novel strategy for soil revitalization through industrial-scale production of enriched vermicompost inoculated with a microbial consortium of nitrogen-fixing Azotobacter vinelandii SA2, phosphate-mobilizing Bacillus megaterium F-1, and fungicidal Streptomyces roseoflavus Str-1. Cattle manure served as the substrate, undergoing pre-fermentation, physicochemical adjustment, earthworm inoculation, and microbial enrichment with high-viability cultures (10⁶–10⁷ CFU/g). Two-season field trials on potato crops in the Akmola region compared enriched vermicompost with classical vermicompost and mineral fertilizers. Key parameters included soil nutrient status, plant growth, tuber yield, and disease incidence. The enriched vermicompost achieved a 27.8% higher yield than mineral fertilizers and a 14.7% improvement over classical vermicompost, while requiring a 60% lower application rate (1.2 vs. 3.0 t/ha). Soil analyses showed increased nitrogen and phosphorus bioavailability and enhanced enzymatic activity, accompanied by reduced pathogen presence and improved tuber storage life. These results demonstrate that integrating microbial biotechnology with vermicomposting generates a biologically active fertilizer that is scalable, cost-effective, and ecologically safe. The technology offers a practical pathway to restore fertility in degraded soils, strengthen plant resilience, and promote climate-adapted agriculture in arid and semi-arid regions.