PASTURE MANAGEMENT INFLUENCES RUNOFF AND SOIL MOVEMENT IN THE SEMIARID TROPICS

The influence of pasture management (sowing introduced species, timber treatment, clearing and cultivation, stocking rate) on runoff and soi l movement was measured on a neutral red duplex soil at Cardigan, near Charters Towers. Runoff and soil movement were greatest in native woo dlands and least in developed pastures, although the differences were often not significant. Runoff and soil movement were related to cover levels on the plots. In small rainfall events (total <50 mm and intens ity <15 mm/h), runoff and soil movement decreased rapidly as cover inc reased, and only small cover levels (40%) were needed to reduce them t o a low level. As the size of the storm increased, greater cover level s were required, and for very large events (total >100 mm and intensit y >45 mm/h) cover had no effect on runoff although it still reduced so il movement. On neutral red duplex soils, managers should maintain at least 40% groundcover but this would still allow large losses of suspe nded sediment in large storms.