Deep-ripper deals with compaction at Mullewa
GroundCover™ Issue: 116 | Author: Melissa Williams
Mullewa brothers Andrew and Rod Messina are no strangers to trialling innovations to lift crop productivity on their deep yellow sandy soils.
They operate ‘Spring Park Farms’ with their father Charlie in a low and variable-rainfall environment and with long-term subsoil compaction and water-repellence issues that undermine crop establishment and production potential on up to two-thirds of the property.
To overcome these challenges, they have adopted technologies such as controlled-traffic farming, strategic deep ploughing, mouldboard ploughing, soil-water probes and the Yield Prophet® decision-support tool.
Until now, cracking a compacted hardpan that typically lies 30 to 40 centimetres below the soil surface and is lower in pH than the layers just above and below has been difficult with conventional tillage equipment and compounded by a lack of big autumn rains that are conducive to deep cultivation.
This is about to change, with the introduction this year of a new deep-ripper – the Gregoire Besson Heliripper – that can slice down to the subsoil at 80cm.“It is enabling us to shatter the subsoil compacted layer, allowing more mineralisation of applied lime to get down through that zone and creating a good environment for root growth,” Andrew says.
“Pits we have previously dug on the farm have shown the bulk of root growth is in the top 30cm, but some plants can get their roots down to one to 1.5 metres – which is where much of the subsoil water is because it hasn’t been accessed for a long time.”
Ripping so deep in ‘one bite’ is helped by the previous shallow loosening of the soil from mouldboard ploughing.
Without this loosening, the very-deep ripping will only form a slot at depth unless there is a shallower leading tyne or a ‘V’ configuration of parabolic tynes.
The Messinas compared the Heliripper with a Grizzly Engineering deep digger (which can rip to similar depths) using a single tyne at 0.5m spacing.
They found 0.5m spacing was sufficient to shatter the ground at depth right across the zone and they preferred the three-point linkage system of the Heliripper.
Andrew says in 12m-wide and 200m-long paddock strip trials on an area that had been mouldboard ploughed in 2011, the deep-rippers produced wheat yields of 2.7 tonnes per hectare, compared with 2t/ha from the nil-treated area and 2.3 to 2.4t/ha from a conventional deep plough (tilling to a depth of 30cm).
“This highlighted that we are still getting a yield response from conventional ploughing to 30cm in the mouldboard-ploughed area – three years down the track – but we got double the response by ripping down to 60 to 80cm,” he says.
A separate 2014 trial of a 12m strip in a paddock that had been mouldboard ploughed in 2013 (and was sown wheat on wheat) found the Heliripper produced double the crop yield – at 1.25t/ha – compared with 0.6t/ha on either side of the trial area, which had no deep-ripping.
Grain quality was unchanged in any of these trials, according to Andrew, who treated about 380ha with the Heliripper prior to seeding this autumn and plans to continue using it across mouldboard-ploughed areas and following broadleaf crops in future years.
“Subsoil compaction at depth is our last soil constraint – aside from adequate rain – and ripping deeper is about the last thing we can do to fix it – aside from building soil organic matter, which we don’t naturally have,” he says.
“For many years we have applied lime at a rate of 2t/ha prior to ploughing and another 2t/ha after ploughing and by doing this we have addressed the acidity problems in much of our topsoil.
“This has increased crop yields by as much as 0.5 to 1t/ha in some years, cut our nitrogen applications to 20 to 50 units of nitrogen per hectare and significantly lowered our weed burden and weed seedbank.
“Now we need to address that zone of 40 to 80cm deep where pH is low and, by deep-ripping parts of the farm before seeding every year, we hope to fix our whole soil profile down to at least 50 to 60cm so that plants can access deep water.”
Andrew says the main drawback of ripping to depths below 30cm is having to use a much smaller machine – the Heliripper is about 6m wide, travels at a speed of 7 to 8 kilometres per hour and treats about 5ha/hour.
He says the machine does not invert the soil, but slices through the ground and does not disturb weeds buried by the mouldboard plough.
A modified very-deep-ripping design is also being trialled at a range of locations in the WA grainbelt by Department of Agriculture and Food, WA (DAFWA), researcher Dr Paul Blackwell this year.
He is testing soil-opening plates for topsoil and/or ameliorant inclusion into the subsoil behind deep-ripping tynes.
Dr Blackwell says this is part of the development of a new deep-ripper and incorporator system being conducted through the GRDC-funded project ‘Minimising the impact of soil compaction on crop yield’.
More information:Andrew Messina
0428 611 464
Dr Paul Blackwell
08 9956 8537
- DAFWA Deep Ripping for Soil Compaction
- Soil Acidity: A guide for WA farmers and consultants by Chris Gazey is available in hard copy from DAFWA
- Liebe Group Deep Incorporation of Lime Fact Sheet
- WA Department of Agriculture: Managing Soil Acidity
- The promise shown by deep-ripping at Mullewa video
GRDC Project Code DAW00243
Region National, West