The reliability and economics of deep-ripping with lime incorporation are being studied by the West Midlands Group.
PHOTO: West Midlands Group
Hot on the heels of a 2013 trial comparing the profitability of different deep lime incorporation methods, the West Midlands Group (WMG) will this year further study the reliability and practicality of these methods for acidic sandplain soils.
Long-term WA research has consistently shown that lime most effectively arrests subsurface acidity (low pH) and lifts crop yields when applied to a depth of at least 30 centimetres and strictly adheres to soil test data.
GRDC-funded trials and the experiences of many growers and agronomists are showing there is potential to fast-track soil pH improvements when lime is mechanically incorporated deeper into the subsurface.
Many West Midlands growers have incorporated lime to depth this summer.
PHOTO: Cox Inall Communications
This is typically achieved during amelioration using deep tillage, spading or mouldboard ploughing to address water-repellency issues.
In 2013, with GRDC funding, the WMG ran a series of side-by-side trials in Dandaragan comparing the productivity and profitability of six mechanical lime-incorporation methods.
Soil test results indicated the deep-ripping, rotary spading and mouldboard ploughing systems successfully incorporated lime into the acidic 20-to-30cm subsurface layer and removed some soil compaction and mild water-repellence issues at the site.
This year, the WMG has started a two-year Council of Grain Grower Organisations-funded project that will further assess deep-ripping modifications plus systems that allow amelioration and liming with stubble retention.
WMG R&D chair and Badgingarra grower John Scotney says modifications include a deep-ripping process that increases the flow of loose, limed topsoil immediately behind the tyne so it is directed into the acidic subsurface.
- About 14.25 million hectares of Western Australian wheatbelt soils are acidic or at risk of becoming acidic to the point of restricting crop yields
- About 75 per cent of agricultural lime used in WA is blanket spread at an even rate on the soil surface – which can be inefficient
- Top-dressed lime can take three to five years to lift subsurface pH levels below 10 centimetres (longer for below 20cm) and improve crop yields
- Mechanically incorporating lime deeper into the soil profile will dissolve the lime more rapidly when it contacts the acid soil layer
“Larger slots behind the deep-ripping tynes will hold the slot open for longer and deliberately direct the flow of loose limed topsoil into the slot,” he says.
“We hope this can have a positive spin-off in reducing the risks of wind erosion by also enabling some stubble cover to be retained after the lime incorporation.”
John says the 2014–16 project aims to help growers in the West Midlands – and potentially across the wheatbelt – introduce robust, reliable and cost-effective systems for broadacre lime incorporation into acidic soils.
He says subsurface acidity is a major issue for many local growers and farm profitability will improve on the back of more reliable lime amelioration techniques that produce a return on capital investment within the first few years of treatment.
Anne Wilkins, West Midlands Group
08 9651 4008
Chris Gazey, DAFWA
0429 107 976
Soil Acidity: A guide for WA farmers and consultants, by Chris Gazey, is available free at:
The Liebe Group Deep Incorporation of Lime fact sheet is available at: www.liebegroup.org.au/wp-content/uploads/2012/01/factsheet-subsoil-acidity-final-12022013.pdf
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