uPtake trials

The uPtake project will establish at least 36 phosphorus fertiliser trials on grazing properties in six regional estuary catchments (Peel Harvey, Leschenault, Geographe, Hardy Inlet, Wilson Inlet and Oyster Harbour). Trials will be 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 phosphorous 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, is being 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.

Selecting trial sites

Trial sites were selected to capture a range of soil types based on their phosphorous buffering index (PBI) and soil phosphorus levels (measured as Cowell 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

2

0 kg/Ha of phosphorus

Basals

3

5 kg/Ha of phosphorus

Basals

4

10 kg/Ha of phosphorus

Basals

5

20 kg/Ha of phosphorus

Basals

6

40 kg/Ha of phosphorus

Basals

7

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

2019

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.

2020

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.
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Trial site locations