POTASSIUM DYNAMICS UNDER DIFFERENT SOIL ORDERS IN INDIA: A REVIEWParamita DebAbstract Potassium plays a vital role in enzyme activation, water relations (osmotic regulation), energy relations, translocation of assimilates, photosynthesis, protein and starch synthesis. Potassium in soil exists in four principal forms -solution K, exchangeable K, non-exchangeable K and structural K; these forms are in a state of dynamic equilibrium. The vast quantity of potassium is removed; 1.5 times more than nitrogen, and Potassium application is significantly lower than that of N or P. In practically all intensive cropping systems in India, the K balance is negative because the addition of K rarely matches its removal, leading in massive K mining. The long-term intensive cropping systems,without K inputs, unfavourably affect K supply for plant uptake, ultimately hindering yield of the crops. In India, soil K fertility is measured using K extracted from neutral normal ammonium acetate but non exchangeable K release with boiling 1M HNO 3 has been noticed to be a better approach for categorising soils for K availability to plants because it offers some useful information on the K-supplying capacity of the soils under continuous cropping systems. The availability of potassium is determined by the overall content, the release properties of its various forms, the presence of clay minerals in varied proportions, and the particle size fractions. Measuring soil K fractions is insufficient for assessing long-term soil K fertility changes; one must also investigate the release properties of native K in terms of Q/I parameters, threshold values, and release kinetics. |