Amanda Pearce1, Malcolm McCaskill2, Ian Ludwig1, Debra Partington2, Rob Norton3, Penny Riffkin2
1 South Australian Research and Development Institute (SARDI), Struan Research Centre, Naracoorte, SA, 5271, http://pir.sa.gov.au/research, Amanda.email@example.com
2 Department of Economic Development, Jobs, Transport and Resources (DEDJTR), 915 Mt Napier Rd, Hamilton, Vic, 3300
3 International Plant Nutrition Institute, 54 Florence St, Horsham, Vic, 3400
Canola and wheat grain yields in the high rainfall zone (HRZ) of southern Australia are currently less than half of the predicted rainfall limited potential. The main barrier to achieving these potential yields is the application of sufficient nutrients. There has been limited research on nutrient response of crops to soil nutrient status conducted in the HRZ. It was hypothesized that grain yields in the south east of South Australia would be limited at soil test levels higher than those currently accepted, as the current critical soil test levels are based on response studies undertaken in regions of lower yield potential. Nutrient omission experiments were undertaken in the HRZ with wheat and canola to assess the impact of particular nutrients on yield under different rates of N supply. A decile 10 season in 2016 saw grain yield responses to Phosphorus (P) and Sulphur (S) of 17 to 38%, respectively over an unfertilised control, where sufficient Nitrogen (N) was applied to meet the expected yield potential. Across the sites tested, the limiting nutrients were first N, followed by P and S. Relative to the 2016 site and season, the current critical values were suitable for P in wheat and S in canola, but too low for P in canola and S in wheat. A decile 1 season in 2015 did not allow full expression of the yield potential achievable in most seasons in this region, with only an N response observed in canola. Further evidence is required to substantiate these findings in less extreme seasons.