Potassium solubilization, plant growth promoting substances by potassium solubilizing bacteria (KSB) from southern Indian Tea plantation soil

A study was undertaken to identify indigenous potassium solubilizing bacteria in southern Indian tea plantation soils. The samples were analysed for various soil edaphic parameters such as pH, Ec, water holding capacity, organic carbon, nitrogen, available phosphorous, exchangeable potassium, exchangeable calcium, sodium and magnesium and potassium solubilizing bacteria were identified. The study revealed that the population density was found to be more in Valparai soils (18.20×104/g of soil) followed by Gudalur and least in Koppa region (5.90×104/g of soil). The population density of KSB in soils of different cultivars of tea plants revealed that higher population was achieved with China hybrids especially UPASI-9 followed by ATK-1, SMP-1 and SA-6.The results indicated that existence of clonal preference by KSB and rhizosphere effect with very good bonding pattern of root systems. About six efficient KSB strains were selected based on its solubilization efficiency in agar and liquid medium. The strains were characterized and identified through biochemical and molecular level. Higher K solubilization (41.91 mg/l) was observed in the KSB strain isolated from Valparai region. In addition solubilization was more when MOP used as K source followed by SOP and Montmorillonite at 5th day of incubation period. Least K solubilization was recorded with GKSB6 (20.31 mg/l). They also proved to produce plant growth promoting substances. These potent indigenous potassium solubilizers were could be used as bioinoculants in tea plantation inturn reduces the usage of chemical fertilizers and improve soil fertility.