Effect of water quality on the leaching of potassium from sandy soil

When potassium (K+) fertilizers are applied to soil, K+ is subject to displacement through the soil profile. More generally, the application of K+ fertilizers to sandy soils with low clay content and small buffer capacity, in which K+ does not interact strongly with the soil matrix, results in localized increases in K+ concentration in the soil solution. Losses of K+ depend on the concentration of Calcium (Ca2+) as a competing ion in the leaching water and the amount of water that passes through the soil. In this study, we examined the adsorption and movement of applied K+ in columns of sandy soil. Glass tubes, 4.8 cm in diameter and 40 cm in length, were packed with either native soil or Ca2+-saturated soil. The resulting 10-cm-long column of soil had a bulk density of 1.65gcm(-3). Native soil was leached with distilled water and CaCl2 solutions of various concentrations. In the Ca2+-saturated soil, a pulse of K+ was leached with CaCl2, Solutions of various concentrations or distilled water. Increasing the CaCl2 concentration from 3 to 15 mm resulted in earlier breakthrough, a higher peak concentration of K ', and greater amounts of leached K. The breakthrough curve for K+, when leached with distilled water, showed very low concentrations and was more delayed than the other treatments. In Ca2+ saturated soil, the amount of K+ leached increased as Ca2+ concentration increased, with LIP to 54% of the added Pulse K+ being removed from 10 pore volumes (Pv) (387mm) of 15mm CaCl2 The presence of Ca2+ in irrigation water and soil minerals able to release Ca2+ is important in determining the amount of K+ leached from soils. Large amounts of K+ are leached from soils in areas where crops are irrigated with water that contains significant concentrations of Ca2+ and other cations. (c) 2006 Elsevier Ltd. All rights reserved.