Characterisation of different forms of potassium in selected soils of West Bengal

Department of Agricultural Chemistry and Soil Science, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur-741 252, India E-mail: sarojsanyal@hotmail.com; sarojsanyal@yahoo.co.in Manuscript received 13 August 2004, accepted 6 March 2005 The exchangeable as well as the non-exchangeable forms of soil potassium (K) were examined in the surface soils of an Inceptisol, an Entisol and an Alfisol of West Bengal, having contrasting properties. The non-exchangeable K in these soils was further fractionated into Step-K and Constant Rate (CR)-K by repeated extractions of these soils with boiling molar nitric acid in a sequential extraction scheme. Potassium release pattern in the given soils varied widely, thereby suggesting a wide range of K supplying capacities of these soils for crop production. Among the soils examined, the pools of water soluble, exchangeable and non-exchangeable K were the highest in the Baharampur soil (an Inceptisol), while these were the lowest in the Susunia soil, an Alfisol. The· Step-K and CR-K fractions of the non-exchangeable K reserve in the present soils also exhibited similar trends. The findings are expected to be of use in suggesting potassic fertilizer application schedules for crop production in the present soils