Phosphate-solubilizing microorganisms of a lateritic soil

Three efficient phosphate-solubilizing microorganisms, isolated from a lateritic soil (Typic Ochragualf), LCB₉, a mixed culture of Bacillus circulans and B. subtilis (B-7648), LCS₄, a Streptomyces sp., and LCF₄, Aspergillus niger van Tieghem were inoculated either alone or in combinations of two with rock phosphate (RP), farm yard manure (FYM), FYM + RP, rice straw (RS), and RS + RP to study their role on the available phosphorus content of the rhizosphere soils and uptake of phosphorus by rice plants (Oryza sativa L. cv. IR-20) and their dry weight at early tillering and preflowering stages of growth in a pot culture experiment with the same soil.

Available phosphorus content of the rhizosphere soils of IR-20 rice increased with application of FYM + RP and with the inoculation of LCB₉, either alone or with LCF₄. Inoculation of LCB₉ + LCF₄ with RS induced the highest uptake of phosphorus by the rice plants and that of LCB₉ + LCS₄ with RP the dry matter content of the plants at early tillering stage, while inoculation of LCB₉ + LCF₄ with RS + RP resulted in the highest uptake of phosphorus as well as dry matter content at preflowering stage. But on an overall basis, the highest uptake of phosphorus and dry weight of the plants were obtained with the inoculation of LCB₉ + LCF₄, whereas in the case of manures the former was obtained with FYM + RP and the latter with FYM alone. Thus, application of FYM, either with or without RP, and inoculation of LCB₉, either alone or with LCF₄, had beneficial effect with regard to accumulation of available phosphorus in the rhizosphere of rice plants, to their uptake of phosphorus and dry matter content. Incidental accumulation of available phosphorus in the rhizosphere was significantly correlated with the uptake of phosphorus by the plants, but not with the dry weight of the plants at early tillering stage, while there was a constantly significant correlation between the uptake of phosphorus by the plants and their dry weight.

Eine Mischkultur aus Bacillus circulans und B. subtilis (LCB₉), ein Streptomyces-Stamm (LCS₄) sowie Aspergillus niger van Tieghem (LCF₄) waren als wirksame phosphatlösende Mikroorganismen aus einem Laterit (typischer Ochragualf) isoliert worden. In einem Gefäßversuch erhielt der gleiche Boden eine Beimpfung mit diesen Mikroorganismen in Verbindung mit Zusätzen von Rohphosphat (RP), Stalldung (FYM), FYM + RP, Reisstroh (RS) und RS + RP. Es wurde geprüft, ob hierdurch der Gehalt an verfügbarem Phosphat in der Rhizosphäre sowie die P-Aufnahme und die Trockenmassebildung von Reispflanzen (Oryza sativa L., Sorte IR-20) im frühen Keimstadium und kurz vor der Blüte beeinflußt werden.

Von den Mikroorganismen erwies sich LCB₉ allein und in Verbindung mit LCF₄ als wirkungsvoll, FYM + RP ermöglichte die höchste P-Aufnahme durch die Reispflanzen, FYM allein erhöhte die Trockenmassebildung am stärksten. Es bestätigte sich die günstige Wirkung einer Beimpfung mit einheimischen bodenbürtigen phosphatlösenden Mikroorganismen, wenngleich nicht alle Ergebnisse signifikant waren.