Biofertilizers have been used as sources to improve plant nutrients in sustainable agriculture. Experiments were conducted to evaluate the potential of phosphate solubilizing bacteria (PSB) Bacillus megaterium var. phosphaticum and potassium solubilizing bacteria (KSB) Bacillus mucilaginosus inoculated in nutrient limited soil planted with pepper and cucumber. Results showed that rock P and K applied either singly or in combination did not significantly enhance soil availability of P and K, indicating their unsuitability for direct application. PSB was a more potent P-solubilizer than KSB, and co-inoculation of PSB and KSB resulted in consistently higher P and K availability than in the control without bacterial inoculum and without rock material fertilizer. Integrated rock P with inoculation of PSB increased the availability of P and K in soil, the uptake of N, P and K by shoot and root, and the growth of pepper and cucumber. Similar but less pronounced results were obtained when rock K and KSB were added concomitantly. Combined together, rock materials and both bacterial strains consistently increased further mineral availability, uptake and plant growth of pepper and cucumber, suggesting its potential use as fertilizer.
-Classical, soluble fertilisers create environmental and economic problems. As an alternative, we studied the direct applications of phosphate rock and potassium rock in conjunction with phosphate-solubilising bacteria and potassium-solubilising bacteria for cultivation of hot pepper Capsicum annuum L. Our findings show that integration of P and K rocks with inoculation of P-and K-solubilising bacteria increased P availability from 12 to 21% and K availability from 13 to 15% in the soil as compared with control, and subsequently improved nutrient (N, P and K) uptake to the plant. This integration also increased plant photosynthesis by 16% and leaf area by 35% as compared with control plants. Similarly, biomass harvest and fruit yield of the treated plants were 23% and 30%, respectively, higher as compared with control. Overall, we found that the treatment with P and K rocks and PK-solubilising bacterial strains and the treatment with classical, soluble fertiliser have a similar effectiveness. Therefore, direct application of P and K rocks and solubilising bacteria is a promising, sustainable alternative to the use of classical fertilisers.hot pepper / phosphate-solubilising bacteria / potassium-solubilising bacteria / mineral uptake / soil availability / acid phosphatase activity
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