Potassium-solubilizing bacteria from tropical forest soils enhance potassium and phosphorus uptake in maize

The continued use of chemical fertilizers to enhance productivity often disturbs the ecological balance of the soil. Integrated nutrient management involving beneficial microorganisms is a promising option for the sustainable maintenance of soil health. In the present study, we aimed to identify potassium (K)-solubilizing bacteria from the tropical evergreen forests of Meghalaya, India, and evaluate their growth-enhancing potential in maize under controlled conditions.

When tested for K and P solubilizing activity in vitro, Bacillus tequilensis NPH2 showed maximum K solubilization (4.71 ± 0.17 mg L^-1), while Priestia aryabhattai NPH4 showed the highest rock phosphate (280 ± 5.2 mg L^-1) solubilization. All the strains were found to produce varying amounts of indole-3-acetic acid, while only two strains (NPH1 and NPH2) produced siderophores. The effect of seed inoculation on plant biometric parameters of maize was variable.

K and phosphorus (P) contents were significantly improved by all the strains. During the pot experiment, treatment with P. aryabhattai NPH4 resulted in the highest available K (35 ± 1.0 g kg^-1 dry weight) and P (3.13 ± 0.01 g kg^-1 dry weight) in maize. Shoot growth of P. aryabhattai NPH4-inoculated maize plants was significantly better than that of uninoculated plants and the positive control.

P. aryabhattai NPH4 was able to survive under acidic to neutral pH, up to 4% NaCl, and temperatures from 15 °C to 45 °C, which can help it to adapt to a wide range of edapho-climatic conditions. The results suggest that P. aryabhattai NPH4 has significant potential as a K-solubilizing microorganism with multifarious plant growth-promoting traits.