Try these new decision support tools to do better in the HRZ

Making fertiliser decisions can be difficult. Paddocks in the HRZ have high yield potential. Actual yields often fall short even in high input cropping systems.

Fertiliser decisions in the HRZ:

  • Under-fertilising appears to be a major cause of yield gaps in the HRZ.
  • You get the best return on nitrogen (N) investment with enough phosphorus (P), potassium (K) and sulphur (S).
  • Critical values for nutrient levels in soil need to be re-aligned for the HRZ.  

Developing new tools to help

Three tools in development could help estimate the most economic rates of fertiliser. The tools support decisions for wheat and canola crops during the growing season. They allow for first-rate decisions at sowing. Then at early stem elongation, you can check top-up rates when yield outlook is clearer.

Fertility response relationships are based on nutrient response trials across the Southern Region. Researchers will continue field trials and gather feedback from advisers and growers. They’ll refine the critical nutrient soil levels and crop yield responses in the tools. In time the tools will become more specific to the HRZ.

These tools are in a pilot phase. They have not been reviewed by the extensionAUS Crop Nutrition CoP. The developers would like your feedback (see below)

Tool 1: Awareness

A quick first look to see how current P, K or S levels could limit crop response to N. It uses input data to estimate how profitable it is to apply N to wheat or canola with different:

  • P, K & S levels
  • seasonal outcomes
  • market prices.

Feedback questions: Do you consider the estimates it provides are reasonable? Is the information easy to follow? Are the terms explained well? Is this useful?

Download the HRZ nutrients ‘awareness’ tool as an Excel file.

Tool 2: Planning

Plan for macro-nutrients (N,P,K,S) to apply at sowing using commodity prices and climate forecasts. The tool offers the opportunity to “top-up” in-crop N application as the season develops.

Feedback questions: Do the at-sowing rates seem reasonable? Are the soil test values appropriate or is there missing information? Is it too simple or too complicated? Is it easy to follow? Does it reflect the responses you have seen in the HRZ? Is this useful?

Download the Planning spreadsheet as an Excel file.

Tool 3: Evaluation

Assess whether nutrients were under or over applied at the end of the season. Look back at the N, P, K and S applications for a crop to check if you used the most profitable combination of nutrients.

Feedback questions: Does this seem reasonable? Is it close to the sorts of application rates used? Are the soil test levels used reasonable from your experience? Is it easy to follow? Is this useful?

Download the HRZ nutrients ‘evaluation’ tool as an Excel file.

Help improve the fertiliser decision tools

We want your feedback on how the tools perform. Did they aid your fertiliser decision making? Give your  comments below


contact Dr. Malcolm McCaskill, Research Scientist – Soils.


Phone: (03) 5573 0957


These decision tools are part of the project:

Optimising yield and economic potential of high input cropping systems in the high rainfall zone (HRZ).




GRDC update paper

 GroundCoverTM: Yield potential rises in the high-rainfall zone

 Production Economics: Are you maximising your profits?




 CropPro wheat nutrition

 CropPro canola nutrition

 Economic Videos: Diminishing Marginal Returns




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