Aspergillus Niger Method of Assaying Available Soil Potassium

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Mangale N.
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It has long been recognized that exchangeable and soluble potassium (K) of soils not receiving potash applications may not sustain satisfactory crop production over extended periods of time (Bray and Deturk 1943; Reitemeir, 1951; and 'MengeJ and Kirby, 1980). Before the advent of the concept of Base Exchange in soils, the immediate source of K was understandably attributed to the breakdown of minerals. It is now a well-established fact that the different forms of soil K (soluble, exchangeable, fixed, and lattice) are interrelated, and comprise a system in which an increase in one form occurs at the expense of one or more 'of the others and in which the net movement may occur from less available to highly available state or vice versa, depending on the particular, stress. Availability of soil K to plants depends on the amount and relative mobility of the different forms, including the rate of replenishment of the depleted immediately available forms by reserve supplies
East African Agricultural And Forestry Journal, 49 (3), p. 78-83