Sustainable agricultural practices using potassium-solubilizing microorganisms (KSMs) in coastal regions: a critical review on the challenges and opportunities

Coastal regions provide excellent ambience for agricultural practices in terms of their weather conditions. However, the presence of salinity in such areas affects crop growth and productivity by restricting the accessibility to vital nutrients. Potassium (K) is one such key nutrient, whose absorption, transport, and distribution to crops are greatly affected by salinity. Conventional use of huge amounts of potash fertilizers in such areas failed to serve the purpose due to their poor mobility, non-availability to the crops and soil precipitation leading to the search for alternate and sustainable approaches. One such approach is the use of potassium-solubilizing microorganisms (KSMs) as plant prebiotics which are capable of solubilizing mineral potassium from insoluble components and thus facilitates the K intake to the crops. Many species such as Aminobacter, Bacillus, Burkholderia, Cladosporium, Enterobacter, Paenibacillus and Sphingomonas are effective K solubilizers. These groups of bacteria are primarily converting the insoluble K to its solubilized form by various mechanisms including the production of organic/inorganic acids, protons via acidolysis mechanism and hydrogen ion-facilitated cation-exchange mechanism. The present review is primarily intended to report comprehensive information on the various negative effects of salinity on crop growth and yield. Also, scientific discussions on the feasibility of sustainable agricultural practices using KSMs were systematically analyzed in the context of their role in actions along with their mechanistic elucidation. Conclusively, this review has critically identified the potential challenges/gaps in the augmentation of KSMs in the coastal regions and provided significant research hotspots to be addressed in future prospects.