Phosphate-solubilizing microorganisms of a lateritic soil

Abstract

Five efficient phosphate-solubilizing microorganisms isolated from a lateritic soil (Typic Ochragualf), LCB₁Bacillus firmus (B-7647), LCB₉, a mixed culture of Bacillus circulans and B. subtilis (B-7648), LCS₄, a Streptomyces sp., LCF₃, an unreported species of Aspergillus, and LCF₄, A. niger van Tieghem, were inoculated in the said soil with rock phosphate (RP), farm yard manure (FYM), FYM + RP, rice straw (RS), and RS + RP in a flask culture experiment to study their role in improving the available phosphorus status of the soil under naturals non-sterile, and partially sterilized conditions. The aspergilli LCF₃ and LCF₄ and the Bacillus LCB₁ showed their efficiency in solubilizing rock phosphate in broth culture. The aspergilli were also efficient cellulose decomposers. Partial sterilization by autoclaving of the soil had no significant effect on available phosphorus content of the soil, irrespective of any inoculation. Inoculation of LCF₄ and LCS₄ increased the available phosphorus content of the unmanured soil. Application of manures, especially that of rice straw, lowered the content, whereas inoculation of LCF₃ and LCS₄ with FYM and that of LCB₉ with FYM + RP increased the available phosphorus content of the soil. However, a significant effect of inoculation was obtained only with LCF₃ and LCF₄ in the respective cases mentioned.

Einem Laterit (typ. Ochragualf) wurde Rohphosphat, Stalldung und Reisstroh einzeln und in Kombination zugesetzt. Von fünf aus diesem Boden isolierten Mikroorganismen erhöhten Aspergillus niger und Streptomyces spec, den Gehalt an verfügbarem Phosphat des unbehandelten Bodens. Alle Zusätze außer Rohphosphat verringerten das verfügbare Phosphat, insbesondere Reisstroh. Signifikante Erhöhungen ergab die Beimpfung mit A. niger und xAspergillus spec. Im einzelnen wirkte Beimpfung mit den beiden Aspergillen in der Variante Stalldung — nicht steril und Beimpfung mit einer Mischkultur von Bacillus circulans und B. subtilis in der Variante Stalldung + Reisstroh — nicht steril deutlich erhöhend auf den Gehalt an verfügbarem Phosphat.