Yield lifts can hinge on better soil moisture know-how

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A woman with laboratory equipment

CSIRO agriculture research scientist Dr Yvette Oliver with water-probe technology that is being used to improve soil water information for Western Australian growers.

PHOTO: Melissa Williams

It is possible to make yield gains of up to 10 per cent by better understanding soil water productivity and improving plant water use efficiency (WUE).

That has been a key finding of the GRDC’s national WUE initiative.

A range of soil-water measuring and monitoring tools and information is now available to help determine how plant-available water capacity (PAWC), start-of-season soil water and soil type impact on crop yield potential.

A 2013 GRDC-funded study into measuring and managing soil water investigated the uptake of these resources, relative costs, information gaps and future Western Australian industry needs.

It found that while there has been good adoption of soil-water technologies through use of modelling systems such as Yield Prophet® and soil-water probes, a lack of knowledge about how to use this information is still impeding more widespread use.

To help close this information gap, the GRDC’s western Regional Cropping Solutions Networks (RCSNs) are this year funding an evaluation of soil moisture monitoring and measuring techniques and how to apply these to yield models.

RCSN western coordinator Julianne Hill says growers and researchers want to know how to get the best ‘bang for their buck’ from these tools.

“For example, what are the benefits of spending thousands of dollars on soil-capacitance probes compared with the benefits of using modelling systems?”

Another initiative stemming from the measuring and managing soil water study has been the establishment of a panel of ‘Soil Water Champions’ in WA.

This comprises researchers from the Department of Agriculture and Food, WA (DAFWA), and CSIRO, members of the GRDC RCSNs, and grower groups, farm consultants and agronomists.

CSIRO agriculture research scientist Dr Yvette Oliver says the project and the new panel will improve coordination and dissemination of soil-water information to growers across WA to use for planning and in-crop decision-making.

She told the 2014 Agribusiness Crop Updates in Perth in February that during the three-year project, researchers will develop simple rules of thumb for a range of soil-water measuring and monitoring systems. This information will also feed into projects to improve crop yields.

“Managing modern farming systems requires an understanding of the relationships between soil-water capacity, subsoil constraints and yield benefits,” she said.

“Factors such as including a long fallow in the rotation, summer weed control, early sowing, water use and canopy management, drought-proofing crops and managing subsoil constraints need to be taken into account.

“Soil-water information is also valuable for making in-season decisions, such as nitrogen top-ups or spray topping.”

Models such as Yield Prophet® and the Agricultural Production Systems sIMulator (APSIM) are increasingly being used in WA to support such crop management decisions.

Other tools, such as MyCrop, CliMate and SoilMapp, are also becoming more popular.

Dr Oliver said to use these tools with confidence required good soil-water information, based on a sound soil characterisation.

“This refers to a measurement of PAWC, soil chemistry (including pH and aluminium levels), soil physical properties and soil classification,” she said.

Soil water characterisations are entered into APSoil/SoilMapp and are available for growers to use in Yield Prophet®.

Useful soil-water and yield-prediction tools for WA conditions

Yield Prophet

  • Yield Prophet® requires a measurement/estimate of soil moisture content at the start of the growing season.
  • It can help optimise nitrogen management, make yield predictions to support grain marketing, help with variable rate fertiliser applications, evaluate inputs versus yield potential in-season and assess the benefits of soil amelioration.
  • There were 234 sites in Western Australia in 2013.
  • Yield Prophet® costs about $500 per year, including $120 for soil analysis sampling.

Other tools

Other tools relating soil water and yield potential include AgSeasons, CliMate, MyCrop, Department of Agriculture and Food, WA’s Potential Yield Calculator, HowWet? and the Agricultural Production Systems sIMulator (APSIM).

Soil-water probes

  • There were about 57 soil-water probes installed across WA in 2013 and more will be installed in 2014.
  • They measure soil water at 15-minute intervals and at 10 to 20-centimetre increments down the profile.
  • Over time, soil-water probes can be used to characterise the soil at these sites.
  • They can cost up to $6000 per site (plus an annual fee) and provide near-real-time data.
  • Data can be linked to Yield Prophet® to compare predicted soil-water estimates with the probe data – but not as a direct input to the model (except for setting the initial water content at the start of the growing season).
  • They offer value in seeing the effects of management and amelioration on the crop’s ability to extract water from the soil at depth and over time.

More information:

Dr Yvette Oliver
08 9333 6469
yvette.oliver@csiro.au

Useful resources:

2014 Agribusiness Crop Updates Papers: www.giwa.org.au/2014-crop-updates

MyCrop and yield constraint calculator: www.agric.wa.gov.au/mycrop

MySoil: http://grains.agric.wa.gov.au/mysoil

SoilMapp: www.csiro.au/soilmapp

South East Premium Wheat Growers Association soil water probe data: www.sepwa.org.au/index.php/2011-11-15-05-40-21/soil-moisture-probes

Precision Agronomics Australia soil water probe data: www.precisionag.com.au/probes_and_prophets.php

The Water Use Efficiency Ground Cover Supplement is available at: www.grdc.com.au/GCS82

A fact sheet on Water Use Efficiency is available at: www.grdc.com.au/GRDC-FS- WaterUseEfficiencySouthWest

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