INTERCROPPING LEGUMES AND NON-LEGUMES TO ENHANCE PHOSPHORUS BIOAVAILABILITY IN DEFICIENT SOILS

Abstract

Phosphorus (P) deficiency remains a critical barrier to sustainable crop production, particularly in calcareous and arid soils where its bioavailability is severely limited. This study investigated the effectiveness of integrating rock phosphate (RP)-enriched compost and plant growth-promoting rhizobacteria (PGPR) within legume–non-legume intercropping systems to enhance phosphorus solubilization, improve soil health, and boost crop productivity. A field experiment employing various treatments—including RP, RP+compost, and RP+compost+PGPR—was conducted under a randomized block design. Results revealed that RP-enriched compost, when inoculated with PGPR, significantly increased available phosphorus in the soil (up to 18.7 mg/kg), enhanced phosphatase activity (up to 38.4 µmol PNP/g soil/h), and boosted microbial biomass carbon levels (averaging 476 mg/kg). Notably, legume crops exhibited higher phosphorus uptake and biomass than non-legumes, particularly under bioaugmented treatments. The soil pH was observed to decline in biologically treated plots, indicating enhanced acidification conducive to phosphate mineral solubilization. PGPR strains demonstrated strong phosphate solubilization zones (up to 15.3 mm), high IAA production (up to 33.4 µg/ml), and significant siderophore activity, validating their role in nutrient mobilization. Intercropping further promoted rhizospheric microbial activity, phosphorus cycling, and overall nutrient use efficiency. Compared to conventional superphosphate application, the integrated RP+Compost+PGPR strategy showed superior performance across all soil and plant health indicators, confirming its viability as a sustainable alternative. These findings underscore the agronomic and ecological potential of biologically enhanced intercropping systems in optimizing phosphorus utilization and reducing reliance on synthetic fertilizers, offering a resilient and eco-friendly pathway for future agricultural practices.