Co-inoculation of potassium solubilizing and nitrogen fixing bacteria on solubilization of waste mica and their effect on growth promotion and nutrient acquisition by a forage crop

Waste mica, a potassium-bearing mineral, is a by-product of mica industry; however, its potassium (K)-supplying capacity for crop production is not well understood. A greenhouse trial was made to study the effect of co-inoculation of potassium solubilizing (Bacillus mucilaginosus) and nitrogen (N) fixing (Azotobacter chroococcum A-41) bacteria on solubilization of waste mica (a potassium-bearing mineral) and their effects on growth promotion and nutrient uptake by a forage crop of sudan grass (Sorghum vulgare Pers.) in a Typic Haplustalf. Results revealed that significantly higher biomass accumulation and nutrient acquisition were obtained in all the pots treated with mica and/or bacterial strain as compared to control. Data indicated that co-inoculation of waste mica with B. mucilaginosus and A. chroococcum A-41 resulted in highest biomass production and nutrient acquisition. Co-inoculation of bacterial strains maintained consistently highest amounts of available K and N in soils even at 150 days of crop growth than other treatments. B. mucilaginosus strain was more effective and potent K solubilizer than A. chroococcum A-41. Thus, co-inoculation of potassium solubilizing and nitrogen fixing bacteria to waste mica could be a promising and alternative option for utilizing this potent source as K fertilizer to crops and maintaining greater nutrients availability in soil. Further studies are necessary to see the effects of these bacterial strains on mobilization of potassium-bearing minerals under field conditions.