Sum16-02 NPK Wheat on Wheat


Part of a continuing trial series to assess how wheat responds to nitrogen (N), phosphorus (P) and potassium (K) fertilizer applications under different conditions,
soil nutrient stores and soil phosphorus buffer Index (PBI) across the wheat belt and, locally, how the response may improve yields.

For further details contact your local Area Manager or the Summit Research Team

Table 1: Soil Analysis
Fig 1: Yield


  • Application of P and N significantly increased yield in this trial and the addition of K, while statistically significant, had less of an impact.
  • Maximum yield and gross margins was seen at N 60kg/ha, P 6-12kg/ha with K 20kg/ha providing a minimal increase.
  • Gross margin impact can be up-to an additional $25 per hectare by selecting the optimal rate of P and an additional $200 per hectare for optimal rate of N.
  • Adequate P nutrition is imperative, promoting early growth and vigour and setting up the crop to utilise applied N efficiently and gain maximum value from in-season N applications.
  • Although frost in the region impacted final overall farm yields, localised areas will have yielded well and potentially, exported significant amounts of nutrients.
    It will be important to consider fertiliser rates in these areas to avoid underutilising yield potential in the coming seasons.
    Soil testing will assist in fertiliser decisions for P and K and continual local research trials will build a foundation of robust and validated data to support these decisions.
  • Achieving optimal productivity means considering adequate and balanced levels of all nutrients rather than a narrow focus on single nutrient.
    Some nutrients, such as P, are only effective when applied at establishment so forming good base nutrition at the start of the growing season
    allows the crop to take maximum advantage of opportunistic applications of in-season top up nutrients to which they will respond.