POTASSIUM SUPPLY CHARACTERISTICS OF 33 SOILS AS INFLUENCED BY 7 RATES OF POTASSIUM

The objectives of this research were to: investigate the relative increases in both Kl (soil-solution K) and Ks (exchangeable K) after addition of graded amounts of a 3-4-7.5 solution fertilizer; and determine if the changes in Kl and Ks with fertilizer additions were related to some measurable physical or chemical property of the soil. The increase in Kl with K addition was described by Kl = axc + d, where x is the amount of added K and a and d are regression constants. Values of c, the curvilinearity coefficient, varied from 1.00 (linear) to 1.59. The increase in Ks with K addition was described by Ks = g + hx, where g represents the amount of exchangeable K in the untreated soil. Values of h, the slope, varied from 0.42 to 1.13. The coefficients describing the relation of both Kl and Ks to added K were not correlated with any of the measured soil properties. -from Authors