Potassium in shrink-swell soils of India.

This article reviews the information regarding potassium (K) status of Indian soils based on research conducted since 1929. The patterns and lacunae regarding potassium consumption in India are also mentioned. The role of minerals in potassium availability vis-à-vis forms of potassium is discussed and elucidated with suitable clay mineralogical evidences. The article also highlights the problems of potassium availability to plants in Indian shrink-swell soils. We have pointed out the inefficacy of the universal method used for assessing plant-available K (1N NH4OAc) in Indian shrink-swell soils, as observed from extensive K response studies. The current practices of assessing only plant-available K is not adequate to detect native changes in soil potassium. This paradoxical situation necessitates revision and revalidation of the existing potassium fertilizer recommendations, which are being adopted since four decades. A holistic research envisaging soil test crop response and mineralogical studies will help in revising potassium evaluation methods in India, leading to judicious fertilizer application by the farmers. [ABSTRACT FROM AUTHOR]