Grower groups band together on acidity

Key points

  • When soil pH is too low – below about 4.8 – some trace elements become more soluble and the concentration of aluminium (Al) in soil water increases rapidly
  • Al is toxic to plants when in solution and reduces root growth
  • Lime can be used to address this problem and lift subsurface pH

Western Australia’s biggest grower groups have joined forces this year to help find the best ways to manage subsurface acidity. It is estimated about 14.25 million hectares across the state’s grainbelt are acidic (with low pH) or at risk of becoming acidic to the point of restricting crop yields.

In recognition of this widespread problem, lime use by growers has increased to record levels. Experience to date shows lime use has potential to:

  • boost crop yields;
  • widen rotation options;
  • lift soil microbial activity; and
  • improve availability of major plant nutrients.

WA growers and researchers have already found that pH improvements can be fast-tracked if lime is mechanically incorporated into the soil subsurface during amelioration. Incorporation methods include deep tillage, spading and mouldboard ploughing.

The application, performance and economics of these systems – and liming rates – are the focus of the new collaborative WA grower group project, funded by the GRDC.

Image of a tractor applying lime

Lime incorporation and spreading rates are being investigated through a series of grower group trials across Western Australia this year.

PHOTO: Travis Hollins, Synergy Consulting

The three-year initiative involves the Liebe Group, the Mingenew Irwin Group (MIG), the West Midlands Group (WMG) and Southern Dirt.

Liebe Group executive officer Clare Johnston says the project is focusing on the best ways to manage soil subsurface acidity in each grower group’s location.

She says the project links growers, researchers, suppliers and natural resource management personnel and is considering the production and environmental effects of measures used to address subsurface acidity.

“Trials set up by the grower groups are investigating the most appropriate strategies that will maximise returns on investment within a few years of treatment and whether these are sustainable,” Ms Johnston says.

Factors being considered include which lime products to use, freight costs, application rates, whether to incorporate lime, how to best incorporate lime, lime quality (including neutralising value and particle distribution), effects on nutrient availability and subsequent fertiliser costs, labour costs and machinery costs.

In 2013, WMG set up a series of large-scale, side-by-side trials comparing the productivity and profitability of six mechanical lime-incorporation methods.

This year, WMG trials are further assessing deep-ripping modifications and flexible systems allowing amelioration and liming with stubble retention, which will have a positive side-effect of reducing the risks of wind erosion.

MIG has established a lime-incorporation trial assessing lime rates of three, six and 12 tonnes/ha, and incorporation with mouldboard ploughing and rotary spading on red heavy soils.

Image of of people doing an earth inspection

Growers inspecting the effects of CalSap® liquid calcium application in the central wheatbelt as part of grower group lime trials this year.

These tillage systems are gaining popularity with sandplain growers in that region and there is much interest in assessing how they perform on red soils.

The Liebe Group is assessing the effectiveness of lime sand, dolomite, liquid lime and granular lime used in combination with different incorporation methods (including mouldboard ploughing, spading, deep ripping, grizzly discs and offset discs).

Research results from the collaborative soil acidity initiative are set to be extended through grower groups’ annual R&D books.

Field days at trial sites may also be held during spring. Check with local grower groups for details.

More information:

Clare Johnston,
08 9661 0570,
clare@liebegroup.org.au

Managing Soil Acidity
www.agric.wa.gov.au/soil-acidity/managing-soil-acidity

Liebe Group Deep incorporation of lime fact sheet
www.liebegroup.org.au/wp-content/uploads/2012/01/factsheet-subsoil-acidity-final-12022013.pdf

Liebe Group soil amelioration calculator
www.liebegroup.org.au/lime-profit-calculator

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GRDC Project Code LIE00008

Region West