Know your ‘bucket’ levels to top-up N

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Brett Robinson from the University of Southern Queensland demonstrated the new GRDC-funded SoilWater App during the GRDC Perth Agribusiness Crop Update.

PHOTO: Cox Inall Communications

Accurate in-season soil moisture and weather information is key to improving tactical fertiliser and grain-marketing decisions in the next few months.

Tailoring inputs to match available soil moisture helps to optimise crop water use efficiency (WUE), yields, grain quality and profits.

Recognising the wide range of soil moisture monitoring/measuring and climate tools now available to Western Australian growers, this year’s joint GRDC and Department of Agriculture and Food, WA (DAFWA), Agribusiness Crop Updates included a focus session centred on the use of this technology.

Many of these new tools are also being applied in a range of projects through the GRDC–DAFWA ‘Soils Constraints – West’ initiative, including tracking and mapping soil moisture and better characterising more than 100 soil types.

Soil water and weather tools

Albany-based DAFWA development officer Jeremy Lemon says decision-support tools can be as basic as weather observations and farm records, or as sophisticated as crop simulation models and web-based reporting of direct soil moisture measurements in-season.

He says sophisticated and complex tools can be limited by spatial variability of rainfall and soils and uncertain season outcomes, including drought and frost. However, easy-to-use, app-based simulations can also improve crop management.

Mr Lemon says crop yield forecasts are a highly valuable first step for assessing season progress and likely outcomes to underpin nitrogen (N) application and forward-selling decisions.

Yield-forecasting tools available in WA include Yield Prophet®, Potential Yield Calculator (PYCAL), N Broadacre and iPaddockYield.

Of these systems, only Yield Prophet® can identify soil plant-available water capacity (PAWC) and current soil water content – or what is in the ‘bucket’.

Mr Lemon says other methods of measuring or simulating soil water include soil water capacitance probes, DAFWA seasonal climate information, the GRDC-funded SoilWater App (scheduled to be available through the Apple Store later this year) and the CliMate app.

“While we can now have a better idea of how much soil water is available for crop growth at any time during the growing season, we are still very dependent on future rainfall because so many WA soils have low PAWC,” he says.

“Many growers use current soil water content to guide N applications, but we also need to know likely response to additional N.

“With estimates of likely yield, N decisions can be supported with tools that incorporate paddock fertility, fertiliser and grain prices to derive optimum economic fertiliser N rates.”

Mr Lemon says in addition to Yield Prophet®, N Broadacre, NUlogic, Fertiliser Optimiser, GreenSeeker/N rich strips and tissue testing are options to boost confidence in decisions.

He says these simulation models, based on weather data and soil description, can be used alone or in combination with direct soil water measurement – such as by using soil capacitance water probes or coring.

Live in-season soil moisture capacitance probe data is available this year for a wide range of sites across the WA grainbelt through the ‘Probes and Prophets’ web page.

A high priority for the GRDC’s Regional Cropping Solutions Networks (RCSN) is a better understanding of soil moisture dynamics – for a range of accurately characterised soil types – and how to best use available data to make in-season (and pre-season) crop-management decisions.

Coordinated by Frank D’Emden, from Precision Agronomics Australia, the RCSN groups have set up a network of soil moisture probes and Yield Prophet® sites across WA.

These provide publicly accessible, real-time soil moisture and weather data and periodic Yield Prophet® reports.

Much of this data is underpinned by soil characterisation research being conducted in WA by CSIRO agriculture research scientist Dr Yvette Oliver through the GRDC-funded ‘Measuring and managing soil water’ project.

More information:

Jeremy Lemon,
08 9803 1120,;

Julianne Hill, RCSN,
08 9726 1373,

Useful resources:
Probes and Prophets:
DAFWA seasonal climate information:
DAFWA season rainfall to date graphs:
SoilWater App:

iPaddockYield App:


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GRDC Project Code USQ00014, KDI00027, CSP00170

Region West, North