Non-exchangeable potassium reserves and their release pattern in some alfisols and inceptisols of West Bengal
2000
Dhar, A. | Sanyal, S.K. (Bidhan Chandra Krishi Viswavidyalaya, Kalyani (India). Dept. of Agricultural Chemistry and Soil Science)
A study was conducted to characterise the non-exchangeable K reserves in three Alfisols and two Inceptisols of West Bengal. The reserves of step-K and constant rate K were evaluated by repeated extraction of soils with boiling molar nitric acid. The reserves of step-K content were, in general, related to the content of the clay fraction of the soils. The cumulative release of non-exchangeable K by repeated extraction with boiling IM HNO3 followed a semi-Iogarithmic behaviour with increasing number of extractions, suggesting that the release of non-exchangeable K decreased with successive number of extractions. The threshold levels of K in soil solution below which the release of K from the initially non-exchangeable K reserve starts were also evaluated for the given soils in terms of the K-activity ratio, K- concentration and exchangeable K in O.OlM and O.OO2M CaC12 solution. These threshold values registered change With the change of background electrolyte concentration. Specifically held K, determined as exchangeable K below which the Gapon constant (KG) showed a sharp rise, varied from soil to soil in almost the same manner as noted for threshold K levels in these soils. These trends have been related to the properties of the soils, especially their clay make-up.
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