Giacomo Betti1, Stephen Davies1
1 Department of Agriculture and Food WA (DAFWA), 20 Gregory St., Geraldton, WA, 6530, agric.wa.gov.au, email@example.com
Clay spreading is a proven method for the amelioration of water repellent soils but it requires high initial capital investment and the outcomes can be quite variable. A field trial at Moora in Western Australia was established in early 2016 on a water repellent sand in order to identify the most cost-effective combination of clay spreading (at 0,100, 150 and 250 t/ha) and subsequent incorporation methods (off-set discs and rotary spader). Results from the first year of the trial showed that spading, on its own or in combination with claying, was the most effective method for reducing the severity of soil water repellence. Early plant establishment however was not significantly affected by the treatments, explained by a wetter than usual weather at seeding and during early plant growth. Nevertheless, clay spreading in combination with spading produced the highest grain yield, up to 1.5 t/ha above the untreated control. The difference in yields between the treatments was partly explained by frost damage. Clay spreading and, in particular, spading were found to significantly reduce frost induced sterility (FIS). Spading alone (without clay spreading) had the highest return on investment (ROI) in the first year thanks to its relative low cost, efficacy in reducing frost damage and good yield response. The trial will continue to be evaluated for a further three seasons (until 2019) in order to better assess the longevity and cost-effectiveness of all treatments in the medium to long term.