Optimising the yield and economic potential of high input cropping systems in the High Rainfall Zone

The High Rainfall Zone in southeastern Australia has high yield potentials for wheat and canola, but growers are faced with challenges about resource allocation in a relatively new and rapidly evolving cropping system. This project will develop tools that predict the production and economic response as well as the risks associated with applying the level of inputs needed for wheat and canola crops to achieve their potential in this region.


01 Jun 2018

2017 Annual Interpretive Summary

Cropping systems have been moving from the low and medium rainfall areas of Australia into the higher rainfall zones, typically those with average annual rainfall of more than 550 mm. The achievable yield potentials in these regions are high (around 8 t/ha for wheat and 5 t/ha for canola), but crop management and cultivar availability is limiting the achievement of those potentials. Since 2014, a collaborative project supported by the Grains Research and Development Corporation has investigated the role improved nutrient management can play in this region. A series of omission trials were conducted along with factorial nutrient interaction experiments to better understand how multiple nutrient limitations can be overcome.

These nutrient response experiments have established that by providing sufficient nutrients, the yield of wheat and canola crops can be equal to or exceed the water-limited potential, except in cases of severe waterlogging or drought. The greatest yield responses across all the sites were to phosphorus (P) followed by nitrogen, sulfur, and potassium. The magnitude of these responses was generally consistent with the expectations based on current soil test critical values, although slightly higher critical values were required for soil test P, compared to research from other regions, to achieve 90% of maximal yield.

These research results were used in an economic analysis, which showed that the 90% critical value underestimated the economic optimum because of the higher yield potential in the HRZ. Since the economic optimum fertilizer application rate is also dependent on input prices, product price and seasonal outlook, three spreadsheets were developed to calculate the optimum rates under a wide range of conditions. The spreadsheets are populated with yield and nutrient response data from a biophysical model, but allow modification to suit individual circumstances.

Trial versions of these spreadsheets can be accessed at http://extensionaus.com.au/crop-nutrition/try-new-decision-support-tools-better-hrz/