The trial will look at four different times and intervals of application throughout the growing season.
The trial has come about in response to farmers looking to better understand the best time is to apply phosphorus in order to optimise productivity, while minimising phosphorus loss and impacts to the environment.
Fertiliser runoff from grazing properties is one of the largest sources of nutrients entering South West estuaries. Improving fertiliser practices to minimise loss off farm will be a major benefit for water quality.
“Farmers are wanting to use fertiliser wisely and to get the best results for their productivity and the environment,” Rob McFerran Project Coordinator said.
“Getting the rate and timing of phosphorus applications right will go a long way to reducing the amount of phosphorus entering Geographe waterways and Geographe Bay.”
The trial, which is being undertaken on a site with a soil type that is highly likely to leach nutrients, will measure pasture productivity and water quality over the growing season via 24 lysimeters that have been installed on the trial site.
Lysimeters are monitoring stations that collect water and nutrients that leach through the soil into purpose-built collection tanks. The leachate volume and nutrient concentration is then measured.
“Understanding how much phosphorus is lost to groundwater is a really important aspect of this new trial,” Mr McFerran said.
“Farmers don’t like to see nutrients or dollars literally being washed down the drain.”
The trial is being delivered as part of the uPtake project, which aims to increase the understanding of farmers and industry in the science of efficient phosphorus application.
At least 36 phosphorus rate trials such as this will be undertaken through the uPtake project across the greater South West.
“uPtake is giving farmers confidence in soil testing and helping them understand the science behind efficient phosphorus application for a given soil type and productivity target,” Mr McFerran said.
“This new trial will provide insights into the best time to apply phosphorus if and when it is needed.”
A second trial will be established in the Geographe catchment in 2022.
The phosphorus timing trial is funded through the Australian Government's National Landcare Program with $445,000 in funding from the State Government's Healthy Estuaries WA program and GeoCatch for soil testing and water quality monitoring.
The project will be delivered in partnership with the Department of Primary Industries and Regional Development, grazing and fertiliser industry groups, and GeoCatch.