Soil phosphorus may form insoluble complexes with some basic and acid cations and become unavailable to plants thus limiting plant growth. Both plants and microorganisms employ different mechanisms to make this phosphorus available to them. A study to isolate and assess phosphate solubilising ability of bacteria in the rhizosphere of grasses from the Seronga floodplains in the Okavango Delta, Botswana was conducted. Tentative phosphate solubilising bacteria were isolated from the rhizosphere and rhizoplane of 20 grasses and shrubs from the floodplains. Out of the many isolates, ten that showed maximum solubilising ability on different phosphate mineral agar were selected and studied further. The solubilisation ability was tested on different agar media containing P in possible soil phosphate complexes i.e., KH2PO4, Mg3(PO4)2, Ca3(PO4)2 using zones of phosphate clearance as a solubilisation indicator. The isolates were able to solubilise complexed phosphate on agar media as shown by the zones of clearance. When the isolates were assayed for their phosphatase enzyme production ability in liquid media and quantified using a spectrophotometer, most showed the ability to produce phosphatase in the medium. Growth in liquid potassium phosphate medium also resulted in a significant drop in pH indicating acid production and lowering of pH as possible mechanisms of phosphate solubilisation. Among the modes of action of phosphate solubilisation tested was the isolates ability to produce organic acids in liquid media. Assaying for the presence of organic acids in the isolates’ growth medium showed that they were able to produce a wide range of organic acids ranging from simple ones such as acetic acid to complex ones such as 3-Hydroxy-2-methyl-3-phenylpropionic acid. This study shows that some Seronga grasses and shrubs harbour phosphate solubilising rhizobacteria which may achieve this by producing organic acids that lower the pH in rhizosphere of the plants. The lower pH in turn results in release of phosphates that were bound by basic cations thus making them plant available. Keywords: Floodplain, grasses and shrubs, microbial organic acids, Okavango Delta, phosphatase enzyme, soils.