Potassium is an essential macronutrient required for the growth and metabolism in plants. Its deficiency causes poor root development, slow growth, low disease resistance, delayed maturity, insufficient seed production, smaller seed production and lower yields. The potassium concentration in soil is little as a major part of potassium exists in insoluble form. It has been further depleted due to the rapid development of agriculture along with an extensive use of fertilizers. In order to mitigate the effects of potassium deficiency, several strains of bacteria and fungi have been identified for their potential of high potassium solubilization. Pisolithus, Cenococcum, Piloderma, Bacillus, Paenibacillus, Acidithiobacillus, Pseudomonas, Burkholderia, Aspergillus and Clostridium are some of the species that release large amounts of potassium from different minerals. These species can potentially enhance the productivity of many crops. This book includes some of the vital pieces of work being conducted across the world on various topics related to the role of potassium in agriculture. Agronomists, educators and students in this field will be assisted by this book.