Practical use of P-solubilization activity of Rhizobium species strains

Besides the nitrogen fixation, some of the Rhizobium and Bradyrhizobium str ains have shown the ability to release soluble phosphates from hardly solub le mineral P compounds. Seven R. japonicum and B. japonicum strains from th e Czech Rhizobia Collection possessing a similar nitrogenase activity and t he effectivity of nitrogen fixation were tested for their P-solubilization activity in liquid shaken cultures. Four of them, which had shown a high P- solubilization activity were used for the production of an innovated Rizobi n preparation. This preparation was then tested in non-sterile soil in a po t experiment, in comparison with strains without P-solubilization activity and non inoculated control. It was shown that the inoculation of soybean wi th Rizobin significantly increased the grain yield in all variants of P fer tilization, in comparison with non inoculated control. The same was true wh en Rizobin inoculation was compared with that inoculated by P-minus strains , except for the variant Fertilized by superphosphate. The inoculation with Rizobin also increased the content of labile P in soil at the end of the e xperiment in variants fertilized by rock phosphate and in non fertilized va riant.