Solubilization of Potassium Containing Mineral by Microorganisms From Sugarcane Rhizosphere

Potassium solubilizing microorganisms (KSM) isolated from sugarcane rhizosphere and their capability on solubilization from some insoluble potassium were examined. Isolation of potassium solubilizer was carried out from three sugarcane plantations area, on Alexandrov's agar medium. From the 41 isolated microorganisms were selected 15 isolates potassium solubilizing microorganisms which exhibiting highest potassium solubilization (solubility index) on solid medium. All the KSM were found to be capable of solubilizing K from insoluble K-bearing minerals source, and the solubilization zone ranging from 0.15 to 4.5 cm. 13.3% isolate has Solubility Index (SI) more than four on solid medium. Quantitative test result of KSM conducted on liquid medium containing potassium mineral trachyte, feldspar, leucite (Pati and Situbondo), released water soluble-K (exchangeable-K) ranging from 0.13 to 12.25 mg.L−1 (Feldspar); 1.24 to 15.57 mg L−1 (Leucite pati); 1.01 to 4.,59 mg L−1 (Leucite Situbondo); and 0.16 to 6,34 mg L−1 (Trachyte). KSM strain Sbr3 caused maximum solubilization on feldspar (12.25 mg L−1), KSM strain Asb3 on leucite Pati (18.17 mg L−1), KSM strain Prj3 on leucite Situbondo (16.14 mg L−1), whereas KSM strain Prj5 caused maximum solubilization on trachyte (6.92 mg L−1). All isolates produced organic acid citric, ferulic and coumaric, some isolates also produced malic and syringic acid. Total organic acid produced by isolated ranging from 130.42 to 434.44 mg.L−1. Ferulic acid was produced by all isolates on all of K sources higher than other organic acid.