Improvement of growth of common bean in phosphorus-deficient soils by phosphate-solubilizing and phytohormone-producing bacteria

The use of phosphate fertilizers is generally required for normal growth and development of crops. The cost of manufactured phosphate fertilizers has increased drastically in recent years and these are becoming out of reach for low-income farmers. The objective of this research was to select phosphate-solubilizing and phytohormone-producing bacteria to improve the growth and P uptake by the common bean (IAC Alvorada) in Red-Yellow Oxisol without the addition of phosphate fertilizer. The experimental design was completely randomized with three replicates and the following treatments: non-inoculated bean plants and plants inoculated separately with seven bacterial isolates: K24, K36, K71, T30, T79, A24, and T22. The previously treated bean plants were grown in the presence and absence of phosphate fertilization. Only the plants inoculated with the isolates K36 and T79 showed higher values for the dry weight and the quantities of P and N uptake by the shoot when cultivated in the absence of phosphate fertilizer. These results demonstrate the potential use of the bacteria T79 and K36 as inoculants for bean plants grown in non-sterilized soil with low available P content, but also indicate that P solubilization may not be the only mechanism responsible for the positive growth response.