Water balance of annual and perennial pastures on a duplex soil in a Mediterranean environment

Abstract

Dryland salinity in southern Australia is largely due to inadequate water use by annual agricultural crops and pastures. Perennial pastures, such as lucerne, have been proposed as a possible means of increasing water use whilst maintaining flexibility in agricultural rotations. In a trial located on a duplex soil near Katanning, Western Australia, lucerne and subterranean clover pastures both used water at rates indistinguishable from potential evapotranspiration during the winter and early spring of 3 consecutive years (1995–97), and completely exhausted water stored in the A horizon. Lucerne, through a deeper rooting pattern and by maintaining activity in the summer and autumn, used approximately 50 mm more water than the annual pasture during each 12-month period. This resulted in reduced deep drainage below 1.2 m in the 1996 season (30 mm compared with 80 mm under annual pasture). With average regional groundwater recharge in the range 10–50 mm, the reductions in drainage observed under lucerne show promise in reducing the regional impact of dryland salinity.