uPtake trials

The uPtake project established 52 phosphorus fertiliser trials on grazing properties in six regional estuary catchments (Peel-Harvey, Leschenault, Geographe, Hardy Inlet, Wilson Inlet and Oyster Harbour). Trials were undertaken on a range of soil types with contemporary pasture species.

Results from the trials will be used to refine national data (Better Fertiliser Decisions for Pastures) used for phosphorus recommendations and to build confidence in industry and farmers in the science supporting fertiliser recommendations. The development of the trials, including site selection, trial design and results analysis, has been overseen by the uPtake Technical Reference Group. Members of the Technical Reference Group include research scientists, farmers, and representatives from government departments, catchment groups, grazing industry groups and the fertiliser industry.

The four years of trials from 2019-23 confirmed that the national critical values for phosphorus are relevant to south-west WA and contemporary pasture species. To learn more about the results, download the trials summary.

The work of the uPtake project continues through related projects including Soil Wise and Healthy Estuaries WA.

Selecting trial sites

Trial sites were selected to capture a range of soil types based on their phosphorus buffering index (PBI) and soil phosphorus levels (measured as Colwell P). This will allow the development of phosphorus response curves (the relationship between pasture production and soil phosphorus levels) for Western Australian soil types.

Trial design

Each trial site is divided into 21 plots, testing seven different fertiliser treatments with three replicates for each treatment (table below). Five rates of phosphorus applications ranging from 0–40 kg/Ha are being tested on plots with and without basal nutrients (nitrogen, potassium, sulphur and trace elements). As the purpose of the trials is to isolate the impact of phosphorus on productivity, basal nutrients are being applied at rates higher than would normally be required to ensure those nutrients are not limiting production.

Two types of trials have been established:

  • Type A – Fenced for the entire season and plots individually mown every 5–6 weeks to determine biomass (to represent a dairy or intensive beef enterprise).
  • Type B – Whole site grazed up until spring, then locked up for biomass measurements (to represent a typical beef hay paddock enterprise).

Treatment 1

0 kg/Ha of phosphorus

Nil basals


0 kg/Ha of phosphorus



5 kg/Ha of phosphorus



10 kg/Ha of phosphorus



20 kg/Ha of phosphorus



40 kg/Ha of phosphorus



40 kg/Ha of phosphorus

Nil basals

Basals are nitrogen (60 kg/Ha), potassium (50 kg/Ha), sulphur (24 kg/Ha) and trace elements

Trial results

uPtake Trial Sites 2019 to 2021

Trial site locations


Nineteen phosphorus trials were established in 2019 across six regional catchments (map below).

Of the 19 trial sites only five responded to phosphorus application, indicating there was already sufficient phosphorus in the soil in the other 14 sites for maximum pasture growth.

Twelve trials were responsive to the addition of basal nutrients (nitrogen, sulphur, potassium and trace elements) indicating that nutrients, other than phosphorus, were limiting production.

The pasture yield results for all 19 trials were consistent with the national data (within 20 per cent of the predicted response). However, national data predicted a phosphorus response on 11 of the 19 trials where only five were responsive. This suggests that the national data for phosphorus recommendations may be higher than required in south-west Western Australia.

Three sites with low pH and low soil phosphorus were less in line with national data which requires further investigation.


Thirteen uPtake trials have been established in 2020 comprising eight new sites and five continuing 2019 sites. Continuing sites will provide additional information on the rundown time of phosphorus in different soil types.
Download 2020 trial results summary


Five new and three continuing trials were established in 2021 through the uPtake project across the greater South West (Peel-Harvey to Oyster Harbour catchments) to examine the response of pastures to phosphorus.

Download 2021 trial results summary

2019 to 2023 results summary 

Over the four years 2019-23 we established a total of 52 on-farm trials. 

Key learnings from the trial results were that:

  • The national critical soil test P values are relevant to south west WA soils and contemporary pasture species
  • Adding P to soils with adequate P will not grow more pasture but will increase the risk of P leaching to the environment
  • Addressing limiting nutrients like nitrogen, sulphur, potassium & trace elements will increase productivity if nutrients are deficient
  • Soil testing is critical to identify nutrients that may be limiting production
  • Applying P following national critical values will optimise productivity, profitability and reduce impacts on the environment
Download 2019-23 trial results summary

Scientific articles

Validation of critical soil-test phosphorus values from the Better Fertiliser Decisions for Pastures meta-analysis
Rogers David, Weaver David, Summers Robert, Dobbe Eric, Master Ronald, McFerran Robert, Mussell Graham, Dawson Luke, Mercy Justin, Richards Peta, Holtham Deborah (2021) Critical phosphorus values from the Better Fertiliser Decisions for Pastures project: early insights from validation trials. Crop and Pasture Science 72, 731-741.
Critical phosphorus values from the Better Fertiliser Decisions for Pastures project: early insights from validation trials

Rogers, D., Weaver, D., Summers, R., Dobbe, E., Master, R., McFerran, R., Mussell, G., Dawson, L., Mercy, J., Richards, P., Holtham, D. (2021) Critical phosphorus values from the Better Fertiliser Decisions for Pastures project: early insights from validation trials. Crop and Pasture Science 72, 731-741.

The project is jointly funded through the State Government's Healthy Estuaries WA and the Australian Government's National Landcare Program with more than $5.5 million funding to improve the health of waterways and estuaries and help increase farm productivity and profitability.