Impact of plant growth promoting rhizobacteria on different forms of soil potassium under wheat cultivation

This study aimed to investigate the effect of some plant growth promoting rhizobacteria with potassium dissolution ability on different forms of potassium in soil under the cultivation of wheat. The factorial experiment was conducted as a randomized complete design with three replications in greenhouse conditions. The treatments consisted of bacterium inoculation (without inoculation, Enterobacter cloacae Rhizo_33, Pseudomonas sp. Rhizo_9, consortium of Enterobacter cloacae Rhizo_33 and Pseudomonas sp. Rhizo_9), potassium application (2·87 mg K kg^-1 of soil and without potassium application).The results indicated that soils treated with Enterobacter cloacae Rhizo_33, either receiving potassium or not, maintain a higher amount of exchangeable K (337 mg kg^-1 ) and water-soluble K (1·25 and 1·31 meq L^-1 with and without K application respectively). The nonexchangeable K and nitric acid-extractable K values were decreased by inoculating bacterial strains. The grain yield was significantly enhanced by the inoculation of bacterial strains irrespective of rates of potassium application. About 19·16% increase of grain yield was recorded by inoculation of Enterobacter cloacae Rhizo_33 and without potassium application. A significantly greater amount of K uptake in grain was obtained in soils treated with Enterobacter cloacae Rhizo_33, with and without the application of potassium (28·7 and 30·7 mg per pot respectively). There was a significant (P < 0·01) and positive correlation between grain yield and grain, shoot and root K uptake. Potassium uptake had a positive significant correlation with water-soluble K and exchangeable K; it was negatively correlated with K (HNO₃ ). The data suggested that inoculation of soil with mentioned bacteria can improve plant growth and potassium uptake. SIGNIFICANCE AND IMPACT OF THE STUDY: As one of the macronutrients, Potassium is the most abundant absorbed cation in most plants and exists in soil in different forms. Soluble and exchangeable forms of potassium (K) are important with regard to plant uptake. K-solubilizing bacteria can convert insoluble potassium to soluble forms; therefore using K-solubilizing bacteria as biofertilizers is a sustainable solution for the improvement of plant growth, nutrition, root growth, plant competitiveness and reducing the use of potassium chemical fertilizer.