Distribution of Potassium in Soils of Manipur Encompassing Physiographic and Hydrothermal Variations

Forms of potassium (K) and their relationship with physical and chemical properties of soils belonging to thermic and hyperthermic thermal regimes, udic moisture regime (hydrothermal regimes) and different physiographic locations covered under the soil orders Entisols, Inceptisols, Alfisols and Ultisols in the state of Manipur were investigated. The water soluble, exchangeable, available, HNO₃ acid soluble and fixed:K in the thermic and hyperthermic regimes constituted 0.05, 1.00, 1.05, 3.97 and 2.72% and 0.07, 1.62, 1.69, 2.69 and 3.24%, respectively of the total-K fraction. In the soils under thermic temperature regime, the acid soluble and total-K showed higher values whereas, in hyperthermic the water soluble, exchangeable, available and fixed K maintained the higher values on an average. The Inceptisols and Entisols showed higher value for all the six fractions as compared to the Ultisols, whereas, the acid soluble and total-K fractions were higher in Ultisols as compared to Alfisols. All the K fractions showed positive correlation with clay and organic carbon in both thermic and hyperthermic temperature regimes except the total K in the hyperthermic regime. The Inceptisols and Entisols under paddy cultivation in the valley flat and valley fill had higher values for all the K fractions. The multiple regression analysis showed that the maximum contribution towards the different forms of K was from the clay fraction whereas the organic carbon had a meager share in the K contribution.