EFFECT OF LANDUSE ON THE COMPOSITION OF THROUGHFLOW WATER IMMEDIATELYABOVE CLAYEY-B HORIZONS IN THE WARREN CATCHMENT, SOUTH-AUSTRALIA

The effect of landuse on composition of throughflow water immediately above the clayey B horizons in duplex soils (mostly natric and/or sodi c) in the Mount Lofty Ranges, South Australia, was investigated using simple lysimeters. During July-November 1991, the pH of the first flow immediately after rainstorm under pines, native woodland, and pasture , respectively, was 5.7, 6.0, and 6.4. At each of the sites, average p H over 4 months during July-November was 5.8-5.9. Both the electrical conductivity (EC) and the amounts of total dissolved solids (TDS) were 2-3 times higher under pine than at other sites. The rate of change i n EC with respect to TDS varied considerably among the sites, possibly due to the large differences in the concentration of dissolved organi c compounds. Although the pH of water was >5.5, both aluminium and iro n were recorded, especially under pine, where there were also high lev els of dissolved organic compounds. High levels of suspended colloidal matter were recorded in the water flowing under pine, and these level s were related to dissolved organic carbon.