TILLAGE METHODS AND SOIL AND WATER CONSERVATION IN AUSTRALIA

Tillage in Australia has evolved from 'imported' European practices to tillage systems more in tune with 'older' fragile soils and more seve re climatic conditions. Cereal yields are commonly limited by water su pply and the native fertility of many soils is poor. Crop/pasture rota tions involving pasture legumes have been the mainstay of cereal produ ction in the winter rainfall areas while production in much of the sum mer rainfall area has relied more on exploiting native fertility. Soil erosion and structural decline are still considered major issues faci ng long-term production. The general trend in tillage methods is for l ess tillage and greater retention of crop residues for soil and water conservation. Tillage experiments have shown that management strategie s involving retention of crop residues (stubble), reduced tillage and crop rotation can reduce erosion and improve yield. Results from exper imentation are highly variable, both in magnitude and direction of res ponses to tillage treatments. Much of this variation is due to variati on in seasonal conditions. Simulation models are being used to examine management options and to design experiments based on a knowledge of climate variability and physical and biological processes.