The present study had as objectives to characterize K forms, plant use of these forms and to evaluate the common bean (Phaseolus vulgaris L.) response to K application in four lowland soils. It was also sought to determine the critical levels for K in soils and plant. The experimental design was completely randomized in a 4 x 5 factorial scheme with four replications. The treatments were a combination of four lowland soils [Mesic Organosoil (OY), Melanic Gleysoil (GM), Haplic Gleysoil (GX), and Fluvic Neosoil (RU)] and five K CEC saturation levels (native, 4, 6, 8, and 10 %). Four bean plants per pot were cultivated until grain production. Soil samples were analyzed for total K, non-exchangeable K, exchangeable K, soil solution K, available K by Mehlich-1 and K extractable by a cation exchange resin. The K quantity/intensity ratio was also determined. The concentration of total and non-exchangeable K were higher in OY and RU soils, while exchangeable K and soil solution K were higher in O and GH soils. The critical K saturation of CEC were 5.0, 4.1, 8.7, and 5.3 % and the critical foliar K levels were 17.9, 30.5, 16.8, and 14.6 mg kg-1 for OY, GM, GX, and RU soils, respectively.
potassium extractors; soil - plant relationship; soil chemistry