QUALITATIVE AND QUANTITATIVE ESTIMATIONS OF POTASSIUM SOLUBILIZED BY TWO POTASSIUM-SOLUBILIZING RHIZOBACTERIA ISOLATED FROM MAIZE RHIZOSPHERE

Abstract

Presently, decline in soil fertility has become a crucial concern to crop farmers in Nigeria.  Only about a few percent of farmers can afford the use of chemical fertilizers to substitute in nutrient deficient soils.  A study was conducted to isolate potassium-solubilizing rhizobacteria (KSR), a group of plant-growth promoting bacteria, from maize rhizosphere.  Root samples were collected from an existing maize plant.  Aleksandrov medium was used for the isolation of KSR by serial dilution method.  Bacteria colonies observed on Aleksandrov plate were isolated and pure cultures obtained.  The results obtained from the molecular analysis, identified two potassium-solubilizing rhizobacteria namely: Lysinibacillus fusiformis and Providencia rettgeri.  Solubilization parameters were determined on colonies which exhibited clear zones of solubilization.  The Gram reactions of both bacteria showed that Lysinibacillus fusiformis was Gram positive while Providencia rettgeri appeared negative.    The zones of solubilization of Lysinibacillus fusiform recorded higher solubilization diameter (5.37 cm) and solubilization efficiency (1400.56 %) than Providencia rettgeri (5.17 cm, 1291.67 % respectively).  Also, the solubilization index was higher in Lysinibacillus fusiformis (2.87) than in Providencia rettgeri (2.17).