Temporal Dynamics of Potassium Release from Waste Mica as Influenced by Potassium Mobilizing Bacteria

Abstract

Potassium mobilizing bacteria (KMB) strains have been isolated from waste mica mines in the Giridih district of Jharkhand, India, using Alexandrov media. These isolates were evaluated for their potential to dissolve water soluble-K from waste mica (muscovite and biotite). Identity was confirmed based on sequencing of 16S rDNA region of those isolates showing promising water soluble-K dissolving capacity. Strains were found to be different isolates of Bacillus cereus, two unconfirmed Bacillus species (strain- 6SB1 and GG6), and one each of B. velezensis and Paraburkholderia kururiensis. Finally, the four most efficient KMB were selected based on their K-mobilizing capability. The K5B (B. cereus) isolate showed the highest K-solubilising capacity in both muscovite and biotite enriched medium. Soil incubation study was conducted using soils of Giridih (Alfisol) with three gradient concentrations of both waste mica tailings and K-solubilising capacity of four KMB isolates (B. cereus, strain- K5B, K6, K15; and Bacillus sp. GG6- K12) were measured at 4, 7, 14 and 21 days intervals. The K release dynamics in incubated soils indicated that potassium was released from both types of micas to significantly higher water-soluble K (WS-K) and exchangeable K (Ex-K) pools due to the inoculation of KMB isolates. Apart from potassium solubilization, B. cereus strain K5B and Bacillus sp. GG6 showed capabilities to produce indole acetic acid (IAA) and gibberellic acid (GA). These results suggested that a combination of KMB strain and powdered mica tailings could be a suitable alternative to commercial chemical fertilizers and maintain soil nutrient status for plant uptake.