Abstract

Soil degradation affects approximately 1.5 billion hectares globally, reducing agricultural productivity and threatening food security. Microbial inoculants represent a promising biological solution for restoring degraded soils through enhancement of soil health and crop performance. This study evaluated the effectiveness of different microbial inoculants on soil health indicators and crop yields across 42 degraded agricultural sites over three growing seasons. Five inoculant treatments were tested: single-strain Rhizobium, multi-strain bacterial consortium, mycorrhizal fungi, combined bacteria+ fungi, and untreated control. Results demonstrated significant improvements in soil health under all inoculant treatments, with the bacteria+ fungi combination showing the greatest enhancement. Soil organic carbon increased by 45-78% depending on treatment, while microbial biomass improved by 125-280%. Enzyme activities including β-glucosidase, urease, and phosphatase increased by 85-195% across treatments. Plant growth-promoting bacteria enhanced nitrogen availability by 65-120%, while mycorrhizal inoculation improved phosphorus uptake efficiency by 85-140%. Crop yields increased significantly under all treatments, ranging from 25% improvement with single-strain inoculants to 68% with combined treatments. Soil aggregate stability improved by 55-85%, indicating enhanced soil structure and erosion resistance. Economic analysis revealed benefit-cost ratios of 2.8-4.7 across treatments, with combined inoculants providing the highest returns. Microbial diversity analysis showed sustained enhancement of beneficial taxa 18 months post-inoculation, indicating successful establishment and persistence. The study demonstrates that microbial inoculants can effectively restore soil health and productivity in degraded agricultural systems, providing economically viable solutions for sustainable land management.