Potassium-Solubilizing Microbes: Diversity, Distribution, and Role in Plant Growth Promotion

TLDR: In this paper, the authors have discussed isolation, characterization, diversity, and distribution of KSM from diverse stresses such as low and high temperatures, acidity, alkalinity, salinity, drought, and plant-associated applications.

Abstract: Injudicious application of chemical fertilizers in India has a considerable negative impact on economy and environmental sustainability. There is a growing need to turn back to nature or sustainable agents that promote evergreen agriculture. Potassium (K) is an important and well-known constraint to crop production. Very low rates of potash fertilizer application in agricultural production lead to rapid depletion of K in the soil. Depletion of plant-available K in soils results in a variety of negative impacts of the crops yield and soil health. Microorganisms play important role in determining plant productivity. For successful functioning of introduced microbial bioinoculants, exhaustive efforts have been made to explore soil microbial diversity of indigenous community, their distribution, and behavior in soil habitats. Soil microorganisms are directly responsible for recycling of nutrients. K is the third major essential macronutrient for plant growth. The concentrations of soluble potassium in the soil are usually very low, and more than 90% of potassium in the soil exists in the form of insoluble rocks. Use of plant growth-promoting microorganisms (PGPMs) helps in increasing yields in addition to conventional plant protection. The most important PGPMs are Azotobacter, Azospirillum, Acidithiobacillus ferrooxidans, Bacillus circulans, B. edaphicus, B. globisporus, B. mucilaginosus, B. subtilis, Burkholderia cepacia, Enterobacter hormaechei, Paenibacillus kribensis, P. mucilaginosus, and Pseudomonas putida potassium solubilizes; these are eco-friendly and environmentally safe. Therefore, the efficient K-solubilizing microbes (KSM) should be applied for solubilization of a fixed form of K to an available form of K in the soils. This available K can be easily taken up by the plant for growth and development. In this chapter has been discussed isolation, characterization, diversity, and distribution of KSM from diverse stresses such as low and high temperatures, acidity, alkalinity, salinity, drought, and plant-associated applications. These studies elaborate on indigenous K-solubilizing microbes to develop efficient microbial bioinoculant for solubilization of K in different conditions of soil which enhances the plant growth and yield of crops.