Levy, G.J., Soil and Irrigation Research Institute, Private Bag X79, Pretoria, 0001, South Africa, Institute of Soils and Water, ARO, Volcani Center, P.O. Box 6, Bet Dagan, 50250, Israel
van der Watt, H.v.H., Dept. of Soil Science and Plant Nutrition, Univ. of Pretoria, Pretoria, 0002, South Africa

We studied the effect of exchangeable K on the hydraulic conductivity (HC) and infiltration rate (IR) of three South African soils and compared it to the effects of exchangeable Ca and Na, using K-Ca and Na-Ca systems with different level of exchangeable K or Na. Increasing the amount of K in the exchangeable phase resulted in a decrease in both the HC and IR of the soils. It was found that, relative to Ca and Na, exchangeable K had an intermediate effect on the HC and IR of the soils. These observations support previous findings in-sofar as HC measurements are concerned and confirm the view that exchangeable K cannot be grouped together with either Ca or Na as ions having similar effects on the hydraulic properties of soils. © 1990 Williams & Wilkins.