Bacillus-Enriched Organophosphorus Biochar Formulations Increase Soil Microbial Diversity and Pigeon Pea Yield

Abstract

Phosphorus (P) deficiency significantly limits pigeon pea growth in acidic soils. Applied P fertilizers tend to diffuse and bind to the active surface sites where they form insoluble complexes with aluminum and iron, rendering the P unavailable for plant uptake. The interactive effects of farmyard manure (FYM), P fertilizers, phosphate-solubilizing bacterium, and maize biochar on P availability and plant growth in acidic soils remain largely unexplored. To enhance P availability in acidic soils, four P fertilizer formulations were developed and tested using pigeon pea as a test crop: (1) biochar-enriched super phosphate and rock phosphate; (2) FYM-enriched super phosphate and rock phosphate; (3) Biochar + FYM-enriched super phosphate and rock phosphate; and (4) Bacillus megaterium-fortified Biochar + FYM-enriched super phosphate and rock phosphate. Field trials were conducted over 2 years to evaluate the effects of these treatments on P availability, uptake, bacterial community dynamics, and pigeon pea yield. The application of B. megaterium (~2 kg) fortified biochar and FYM-enriched rock phosphate at 750 kg ha⁻¹ significantly improved soil available P (10 mg kg⁻¹), P uptake (21.7 kg ha⁻¹) and Bacillus population (16% higher) compared to super phosphate alone. This formulation also enhanced acid phosphatase activity, microbial biomass phosphorus, biomass carbon, and microbial community composition, contributing to improved plant growth and seed yield (1558 kg ha⁻¹). The combined application of B. megaterium (2 kg) and 50 kg P in biochar-FYM-enriched rock phosphate at 750 kg ha⁻¹ demonstrated a sustainable approach for increased phosphorus availability and uptake in low pH soils. This eco-friendly strategy improved pigeon pea production and reduced reliance on chemical fertilizers, presenting a viable solution for sustainable P management practices in acid soil.