Potassium Dynamics and Role of Non-exchangeable Potassium in Crop Nutrition

摘要

Potassium is among the abundant nutrient elements in the earth's crust and also the nutrient removed by crops in large amounts. Potassium in soil exists in four principal forms - solution K, exchangeable K, nonexchangeable K and structural K; these forms are in a state of dynamic and complex equilibrium. Potassium availability to crops is commonly assessed using the ammonium acetate method, which estimates the amount of K present in the solution and exchangeable forms. However, the nonexchangeable form of K contributes significantly to crop K nutrition, especially in the intensive cropping systems. Potassium fertiliser recommendations developed on the basis of the status of both exchangeable and non-exchangeable K lead to more efficient and profitable use of imported K-fertiliser. Mica-poor red and lateritic soils of Southern India and acidic soils in Eastern and North Eastern India require regular K additions. Intensive cropping systems and K exhaustive and quality crops require optimum K nutrition. Based on the status of exchangeable and nonexchangeable K, districts in India were grouped into 9 categories and category-specific K recommendations were suggested for sustainable management of potassium in the Indian soils and crops. Rationalization of fertiliser use based on identification of K-efficient zones considering both fractions of K improves K use efficiency and ensures higher crop production.