Melissa Fraser 1, David Davenport 1, Nigel Wilhelm 2 and Brett Bartel 1
1 Rural Solutions SA, PIRSA
2 South Australian Research Development Institute, PIRSA
• Crop productivity on infertile sandy soils can be greatly improved by incorporating organic matter deep into the soil (>30 cm).
• In some cases, crop yields are further boosted with the incorporation of clay and/or fertiliser to depth.
• Two years of recent research show that the best soil modification treatments can increase crop yields by 70 to 200 %, even in challenging seasons.
• Treatments that address multiple constraints in these soils provide greater benefit than those addressing individual issues.
• Crop yields are reduced when clay is poorly incorporated into the soil.
Up to 40 % (4.1 million hectares) of the broadacre farming area of South Australia has soil constraints that could be overcome through the application of new advances in technology, machinery and soil management. These include non-wetting sands with low fertility and low water holding capacity and heavier soils with poorly structured subsoils.
‘New Horizons’ is a South Australian Government funded program developed to capture an additional $800 million in agricultural production per annum in South Australia from these badly constrained soils. In 2014, three trial sites were established on sandy soils on the Eyre Peninsula, Murray Mallee and South East; at Brimpton Lake, Karoonda and Cadgee respectively. The sites all have sandy A horizons with a clay B horizon deeper than 30 cm. A range of treatments were applied to overcome constraints including water repellence, low water holding capacity and poor fertility. These treatments included the addition and incorporation of clay, fertiliser and organic matter, and combinations of these. The aim of this research was to confirm that crop productivity can be substantially improved when subsoil chemical, physical and biological constraints in sandy soils are treated. The impact of these treatments on crop production and soil condition has already been monitored for two years and we hope to continue these trials for several more seasons to measure their ongoing benefits.