Phosphate Solubilizing Microorganisms From Tropical Soil and Their Ability to Enhance Nutrient Uptake In Rice.

Uplands constitute 60 % of the rice-growing environment in Ghana. The traditional upland rice-based cropping system relies on a period of fallow to restore soil fertility and this is unable to maintain soil organic matter, nitrogen and phosphorus thus resulting in decline of upland rice yield.

 The objective of the study was to use phosphate solubilizing microorganisms (PSMs) and rock phosphate (2 % available P) to build up soil phosphorus and also improve the yield of rice.  Fifty-two isolates, mostly bacteria, fungi and actinomycetes have been obtained. They are mostly Gram negative and can solubilize rock phosphates in cultural solution. One of such isolates produced 80 mg/l of available phosphate from rock phosphate in culture solution within 2 weeks. Initial pot experiment showed that rice yield, N and P uptake were significantly (p < 0.03) influenced when rice was grown in soil of pH 4.5-5.7 with some of the isolates. Using PSMs and rock phosphate to grow upland rice in the field condition for two years, results showed that the treatment where Triple super phosphate (TSP, 45 kg P₂O₅/ha ) + PSM was used, had the highest rice grain yield (p < 0.05) as compared to using only TSP(45 kg P₂O₅/ha)  to grow rice. In such field experiments, basal nitrogen and phosphate fertilizers had been applied previously. Also, treatment of 22.5 kg P₂O₅/ha TSP +22.5 kg (P₂O₅/ha) rock phosphate +PSM inoculum, the yield of rice improved significantly, staw weight was high and had heavy grain ear as compared to that of TSP applied at 45 kg P₂O₅/ha. There is a synergistic interaction between PSMs and TSP that favorably enhanced plant growth. PSMs from the tropical environment used for this experiment, helped build up soil nitrogen and soil organic matter thus sequestering more carbon from the atmosphere.