Whole farm nutrient mapping

Page last updated: Thursday, 29 November 2018 - 8:50am

Whole farm nutrient mapping helps graziers make informed nutrient management decisions. Presenting soil test results as colour-coded nutrient maps, together with the data, has more successfully met partners', participants' and industry needs. This approach has been used in the greater than 600mm rainfall areas of south-west Western Australia.

This page describes the whole farm nutrient mapping procedure and provides links to supporting information.

Whole farm nutrient mapping: saving $ and the environment

Whole farm nutrient mapping (WFNM) helps graziers make informed nutrient management decisions. By using soil test results, nutrient use can be optimised to increase profitability and reduce nutrient run-off to nearby waterways. The video below explains the work and one farming family's experience.

Another farmer's experience of the WFNM system

Neville Haddon, a user of WFNM, said;

“The whole farm nutrient maps are one of the most useful tools we have. We consult them often. The coloured maps are dramatic and it really hits you between the eyes. They are extremely effective at grass roots level and whoever came up with them deserves a medal. The maps showed a group of high phosphorus, high potassium, but acid paddocks around the dairy to which we have since only applied lime, nitrogen and sulfur. The economics of savings on unnecessary fertiliser is significant, and the intensity of the sampling gives us confidence. We have had no decrease in production using this strategy.”

How WFNM works

WFNM is based on:

  • collecting a representative sample for each paddock on the whole farm
  • analysing each sample for phosphorus, potassium, sulfur, phosphorus buffering index and pH
  • assessing the soil test data against nationally agreed critical values
  • preparing colour-coded maps to assist in fertiliser decision-making
  • running workshops to improve graziers' understanding of nutrients in the landscape, interpretation of soil test results, and use of nutrient maps.

Getting nutrient delivery right

The evenness of fertiliser application is important for getting the best production responses in a paddock. Unfortunately, not all spreaders work as indicated, and not all users set up their spreaders correctly.

We have held AccuSpread fertiliser spreader demonstration days on farms to show the difference between spreaders, the variation between how individual spreaders applied fertiliser across the paddock, and how to make changes to improve the evenness of application – to help graziers with the 4Rs: right source, right rate, right time, right place.

The WFNM process has been assessed and approved as an interpretation system under Fertcare®. This means that the maps produced as part of the WFNM process will now sport the Fertcare® logo, which provides assurance that industry standards are consistently met.

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Some common findings from WFNM

Sampling of more than 160 000 hectares within the south-west of Western Australia using WFNM principles shows some common themes:

  • Phosphorus levels are higher than needed for pasture growth at 90% of maximum production on over 70% of paddocks. Those paddocks with excess phosphorus have 1.6–2.1 times the amount of phosphorus needed in the soil.
  • Over 80% of tested paddocks have acid surface soils (i.e. pH <5.5 in calcium chloride in the top 10cm of soil). While this is a factor in many soil interactions, there is less of an impact on phosphorus availability than may be currently assumed. 
  • Over 25% of all paddocks tested were deficient in potassium, with more phosphorus than needed.
  • Using the soil sulfur test, 13% were sulfur deficient while having excess phosphorus in the soil.

These results are consistent with other sampling programs undertaken throughout the south-west. This indicates that fertiliser management needs changing, with a greater emphasis on addressing limiting factors, such as acidity, and potassium and sulfur deficiency.

WFNM recommends soil testing to inform fertiliser decisions. Only apply nutrients you need and focus on the most limiting factor.

What next?

We are continuing WFNM work in partnership with the Department of Water and Environmental Regulation under the Regional Estuaries Initiative - Sustainable Agriculture program. This work is relevant to all grazing industries within the greater than 600mm rainfall zone, not only the estuarine catchments.

For more information

For up-to-date WFNM activities, visit the WFNM Facebook page.

For more details, email nutrientmapping@dpird.wa.gov.au.

Contact information

Peta Richards
+61 (0)8 9777 0144