Research Projects

Potassium (K) is a crucial nutrient in soils, with its origin, distribution, and dynamics influenced by the weathering of K-bearing minerals. K-feldspars, muscovite, and biotite are the principal K-bearing minerals found in India's major soils. The current method for determining soil available K is 1N NH4OAc extract, but this method often shows anomalous crop responses to K fertilizers. This issue is prevalent in semi-arid tropical (sAT) climates, where soils contain high amounts of K-bearing minerals. The release of K in sAT soils depends on the K-selectivity of the K-bearing minerals, and mass exchange is governed by mass exchange rather than diffusion. To understand the contribution of K from various K-bearing minerals, K release from colloidal exchange sites needs to be done using a strong exchanger like BaCl2. Non-exchangeable K, extracted by boiling nitric acid, shows a good correlation to crop response, but most K is released via cation exchange and the remainder via mineral structure dissolution. K release from K-feldspar and muscovite is insufficient to meet crop demand at peak periods. Therefore, suitable methods to quantify soil biotite content are needed to predict the long-term K supply capacity of soils and reduce the import burden of K fertilizers, thus saving foreign reserves.