Potassium reserves in the world. Potassium fertlizer technology. Preparation of finished fertilizers containing potassium. Agronomic evaluatin of potassium polyphosphate and potassium calcium pyrophosphates as sources of potassium. Mineralogy of soil potassium. Role of potassium in photosynthesis and respiration. Effect of potassium on carbohydrate metabolism and translocation. The effect of potassium on the organic acid and Nonprotein nitrogen content of plant tissue. The effect of potassium and other univalent cations on the conformation of enzymes. Role of potassium in human and animal nutrition. The effects of potassium on disease resistance. Effect of potassium on Quality factors - fruits and vegetables. Soil factors affecting potassium availability. Mechanism of potassium absorption by plants. Exchangeable cations of plant roots and potassium absorption by the plant. Interaction of potassium and other ions. Plant factors affecting potassium availability and uptake. Potassium nutrition of tropical crops. Potassium nutrition of forage crops with perennials. Potassium nutrition of soybeans and corn. Potassium nutrition of tree crops. Potassium nutrition of vegetable crops.