LEACHING RATES UNDER A PERENNIAL PASTURE IRRIGATED WITH SALINE WATER

Dilution of saline groundwater (2. 5 dS m** minus **1) for irrigation is a common practice in the Shepparton Region of Northern Victoria. There is little information describing the leaching rates and hence longterm soil salinity levels that will result from such practices. There is also little information to suggest the effect of irrigating with saline water on groundwater recharge. Leaching rates under perennial pastures grown on a Paleustalf were estimated using three methods based on the mass conservation of chloride. Five treatments were irrigated with water ranging from 0. 22 dS m** minus **1 to 4. 84 dS m** minus **1. Leaching rates were greater the higher the salinity of the irrigation water. Increased leaching resulted from both increased electrolyte levels in the water and decreased water uptake by plants. A model based on non-steady state solute movement usefully predicted the approach of steady-state conditions in the root zone.