Distribution of potassium fractions in relation to different physiographic units of Haryana, Northwest India

The distribution of potassium (K) in soils varies across physiographic units due to differences in the intensity of soil-forming factors and processes within each unit. Therefore, we aimed at finding out the relationship between the forms of K (K forms) with physiographic units and the association of K forms with soil properties in the northwestern region of India. For this, horizon-wise soil samples were collected from pedons and soil samples were analyzed for physico-chemical properties and K forms. The results revealed that soil texture varied from sand to clay loam across the pedons. The soils were slightly to strongly alkaline in reaction (pH, 7.8-8.6) with cation exchange capacity (CEC) ranging from 3.51-17.74 cmol (p⁺) kg^-1. The water-soluble potassium (WSK) ranged between 0.016-0.064 cmol (p⁺) kg^-1, exchangeable potassium (EK) between 0.07-0.41 cmol (p⁺) kg^-1, fixed potassium between 0.73-3.70 cmol (p⁺) kg^-1, lattice K from 30.29-48.48 cmol (p⁺) kg^-1 and total potassium from 31.03-52.18 cmol (p⁺) kg^-1 in different horizons of pedons across the physiographic units. Water-soluble K and EK decreased with soil depth whereas fixed K and total K varied irregularly with depth. By and large, the results revealed that all the K forms followed the trend: old alluvial plains > recent alluvial plains > Shivalik hills valley > Shivalik foothills > piedmont plain > aeolian plain. The positive and significant correlation was observed among different forms of K which indicates the existence of interdependency and dynamic equilibrium among K forms.