South coast soils turned upside down
GroundCover™ Issue: 122 | 02 May 2016 | Author: Melissa Williams
Esperance growers Ashley Reichstein and Megan McDowall are using a new deep-ploughing system to ‘reset’ soils affected by compaction, acidity and water repellence across their farm. After grappling with expanding areas of poorly germinating crops due to these constraints in recent years, they have invested in a TopDown cultivator.
As the name suggests, in one pass this machine can break up soil to a depth of 30 to 40 centimetres, bring subsoil clay closer to the surface and mix topsoil organic matter down into the profile.
Initial trials in 2015 with local Department of Agriculture and Food, Western Australia (DAFWA) senior research officer David Hall resulted in seven to eight per cent higher canola yields of 2.1 tonnes per hectare where the TopDown cultivator was used, compared with yields of 1.94t/ha in an untreated control area.
At a canola price of $580/t, this extra 0.16t/ha was worth about $91/ha in net returns (minus net costs).
Ashley says the canola crop sown into the TopDown-ploughed area produced about 0.3t/ha more biomass and had vastly improved root systems.
“Where we used the machine, the canola roots had penetrated to a depth of 18cm in the first four weeks after sowing, compared with 8cm for canola roots in the untreated area,” he says.
“We had spread lime at the trial site only two years before and soil pH at depth was quite good.
“By bringing subsoil to the surface, we increased the topsoil pH from about 4.5 to 5. There may also be nutrient benefits in mixing up topsoil and subsoil to stimulate more natural nitrogen release, which could be particularly useful in years with a dry finish – where yield benefits would potentially be a lot higher.
RCSN soils forum
Ashley outlined his early success with the TopDown cultivator at a GRDC Regional Cropping Solutions Network (RCSN) Esperance Port Zone soils forum earlier this year.
Ashley says they aim to treat the majority of their 4800ha property in the next few years, including soils with clay to a depth of 25 to 30cm.
“The aim is to mix up and incorporate the high levels of surface organic matter we have from no-till and stubble retention, pull up subsoil clay to the surface and make ourselves a deeper, much higher-quality topsoil,” he says.
“With subsoil compaction and other constraints of acidity and water repellence affecting 80 to 90 per cent of our sandy gravel and sandy loam over clay soil types, we currently only have a rooting depth topsoil of about 15cm.
“We want to double that to 30cm to really improve crop germination, especially if there is marginal moisture at the start of the season, and lift crop yields.”
Ashley estimates the TopDown cultivation system costs about $60/ha, which he says is great value for a single-pass operation that is required maybe only once every eight to 10 years and that resets the soil profile.
He says he is moving towards implementing full controlled-traffic farming to prolong and protect the benefits of this amelioration system. His machinery/implements are matched to 12, 18 and 36-metre operating widths.
How it works
Ashley and Megan sourced a Vaderstad TopDown 600 cultivator with a cut width of 5.8m that can work directly behind a harvester if desired.
The machine has two-way front discs that are independently operated, work to a depth of 10 to 15cm, and incorporate harvest trash and mix this through the surface to breakdown.
“Behind the discs, we have tynes spaced at 280 millimetres that plough to a depth of 30cm, bringing clay to the surface, busting it up and spreading it through the soil profile,” Ashley says.
“Then we have set up, on every second tyne on the last row, a 50mm-wide deep loosening point at 75cm spacing to dig and disturb down as far as 40cm in some areas. This set-up does need more horsepower, but generally we are pulling the machine with a 475hp tracked tractor and operating at ground speeds of about seven to eight kilometres per hour.”
Ashley says the TopDown cultivator has consolidation – or press – wheels at the rear to close the furrow and compact the ground to a smooth surface.
Where to next
Ashley says this year and beyond he and Megan will continue to use the TopDown plough across the property on the back of summer rainfall and in the lead-up to sowing.
He says there may be opportunities in future to treat sandier, water-repellent areas in one pass and incorporate early seeding of canola.
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Useful resources:Deep ripping fact sheet
GRDC Project Code DAW00242
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