Rock phosphate composted with farmyard manure and phosphate solubilizing bacteria boosts maize yield in alkaline...

Phosphorus (P) availability is severely limited in alkaline calcareous soils due to fixation with calcium and magnesium, which restricts its uptake by crops such as maize. Rock phosphate (RP) is an affordable, eco-friendly P source, but its slow dissolution restricts its use in such soils. We hypothesized that pre-treating RP through co-composting with farmyard manure (FYM) and phosphate-solubilizing bacteria (PSB) could enhance P availability, soil fertility, and maize productivity. FYM was composted with RP and single superphosphate (SSP), with or without PSB, for 60 days, then applied to maize (Azam cultivar) at 90 kg P₂O₅ ha⁻¹ in a randomized complete block design conducted at an agronomic research farm of University of Agriculture Peshawar Khyber Pakhtunkhwa Pakistan in 2023. The FYM + RP+PSB compost produced the highest plant height (136.4 cm), grain yield (3427 kg ha^- 1) and biomass (9783 kg ha^- 1), all exceeding those of SSP alone ( p < 0.05). Plant P uptake (19.6 kg ha^- 1) and post-harvest soil available P (3.76 mg kg^- 1) was higher under FYM + RP+PSB compost indicating enhanced soil fertility. Phosphorus use efficiency of RP increased significantly (p < 0.05) from 4.24% (sole RP) to 13.24% (FYM + RP) and 23.15% (FYM + RP+PSB). These findings suggest that co-composting RP with FYM and PSB is a cost-effective and sustainable strategy to improve P availability and maize productivity in calcareous soils, reducing dependency on chemical P fertilizers.