Studies on Phosphate-Solubilizing Bacteria in Soil and Rhizosphere of Different Plants

Occurrence of bacteria (total), acid producing and phosphate dissolving micro-organisms in soil, rhizosphere, and rhizoplane of Egyptian cotton, peas, or maize during their different growth phases was studied. The rhizosphere effects were generally positive and differed according to type of plant, growth phase of each special plant, and type of micro-organism under study. The high densities of bacteria, acid-producers, and phosphate-dissolvers in the rhizoplane samples suggest the conclusion that roots of the studied plants are colonized with these soil micro-organisms. The role of the micro-organism and the mechanism of the noted colonization is not fully understood yet. However, the presence of high numbers of bacteria in the rhizosphere zones of all plants is undoubtedly important, since they may convert organic and inorganic substances into available plant nutrients. The acidproducing organisms were greatly stimulated in the rhizosphere of all plants. Consequently, the production of acid, especially in alkaline soils such as in Egypt, may directly or indirectly react with insoluble inorganic compounds, converting their nutrient elements into available forms for the growing plants. But not all acid-producers are considered as phosphate-dissolvers. Therefore, the presence of high numbers of phosphate-dissolving bacteria in the rhizosphere zones may explain how the growing plants can obtain their requirements in such alkaline soils.

Der Khizosphäreeffekt war für alle Mikroorganismengruppen positiv. Rhizosphäre und Rhizoplane wurden durch Bodenbakterien besiedelt.

Am höchsten wurden die Säurebildner in der Rhizosphäre stimuliert, was für die alkalischen Böden Ägyptens vollkommen logisch erscheint.

Nicht alle Säurebildner konnten Phosphate auflösen. Die Anwesenheit vieler phosphatauflösender Bakterien in der Rhizosphere wachsender Pflanzen kann zur besseren Versorgung der Pflanzen mit aufnehmbarem Phosphor beitragen.