Frank Valzano. Interactions influencing sodic soil water availability and aeration in dryland cropping and horticultural systems Sodic soils are usually defined as consisting of an exchangeable sodium percentage greater than 5 or 6 %. These soils tend to occur within the arid to semi-arid regions of Australia. They may, however, be present to a lesser extent in higher rainfall areas. Approximately one-third of the Australian continent is exposed to the deleterious effects of sodicity. Sodic soils are often too wet or too dry for optimal plant growth. The mechanisms influencing soil water availability and aeration need to be examined under a variety of soil types and management regimes as a means of developing a more complete understanding of sodicity. Consequently, this study aims to examine relationships between sodic soil field behaviour, and soil water availability and aeration in three different localities. The effects of differing lime, gypsum and cultural treatments on these relationships and on soil conditions will also be determined. As a means of achieving these aims, three areas within Australia with distinctly different sodic soil types and management regimes have been selected. These areas include Peak Hill NSW, Carnarvon WA and Natimuk Victoria. Initial results suggest that sodic soil water availability increases significantly following the application of either lime or gypsum. A tillage-chemical ameliorant interaction was present. Other factors such as soil clay mineralogy also appear to be influencing water availability in these systems. A single application of lime will have longer lasting beneficial effects on acid-neutral sodic soils than the application of gypsum. Combinations of lime and gypsum, however, deliver both short and long term benefits.

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