Rhizosphere microbes: Potassium solubilization and crop productivity – present and future aspects

Abstract

The plant rhizosphere harbor array of potassium-solubilizing microbes (KSMs), which solubilize the insoluble and inaccessible potassium (K) to accessible forms of potassium for plant uptake and transport, is one of the inevitable elements for growth and yield. The process of potassium solubilization is performed by specific rhizosphere microbes, which include bacteria and fungi; the prominent are Bacillus sp. (B. megaterium, B. mucilaginosus, B. edaphicus, B. circulans, Acidithiobacillus ferrooxidans, Pseudomonas putida, Arthrobacter sp., and Paenibacillus sp.) Aspergillus spp., and Aspergillus terreus. The agricultural soil particulates contain minerals such as orthoclase, illite, biotite, feldspar, and mica which contain potassium, though this is not available to the plants due to its immobilized form. Intermittently, potassium is an important element after N and P in soil chemistry; therefore, the rhizosphere microbes play a significant role in mobilizing the unavailable form of potassium to the plant roots. The potential rhizosphere K-solubilizing microbes such as Pseudomonas, Bacillus, and Aspergillus excrete organic acids, which solubilize the unavailable potassium and make available to plant roots. Till date, most of the work has been done on nitrogen-fixing and phosphate-solubilizing microbes; moreover, the available biofertilizer with solubilized K (readily available) needs more attention at commercial scale. The current chapter addresses the information gaps related to potassium-solubilizing/potassium-mobilizing microorganisms in soil and analyzing current and future aspects of potassium-solubilizing microbes for the crop productivity.