Perspectives of potassium solubilizing microbes in sustainable food production system: A review

Potassium is a major essential plant nutrient that plays a pivotal role in plant physiological and metabolic processes, and provides resistance against biotic and abiotic stresses. In order to feed an ever increasing world population, cultivation of high yielding varieties in an intensive production system during the last few decades caused depletion soil fertility status, especially potassium (K). As 90-98% K reserves in soil system are non-exchangeable mineral sources, efficient rhizospheric microbes (ERMs) are needed to effectively dissolve this mineral and make it available to plants. A diverse group of ERMs such as rhizobacteria (Bacillus edaphicus, B. mucilaginosus, Acidothiobacillus ferrooxidans, B. circulans, Paenibacillus sp.), fungal strains (Aspergillus terreus and Aspergillus sp.) and nitrogen fixing rhizobacteria (NFR) is involved in K mineral (orthoclase, muscovite, feldspar, biotite, mica, illite) solubilization. Mechanisms utilized by microbes for K dissolution are organic acid production, lowering soil pH, acidolysis, chelation, exchange reactions and complexation. These ERMs also contribute to other beneficial effects such as production of growth hormones, nitrogen (N) fixation, phosphorus (P) dissolution, enlargement of root system and antibiotic production. More specifically, potassium solubilizing microbes (KSMs) are being commercialized in the form of biofertilizer and inoculum to alleviate constraints of chemical fertilizers. This is an ecofriendly approach towards sustainable food production systems in many countries of the world. This report updates our current knowledge and potential for developing microbial based products.