Yorkrakine grower Colin Hutchinson.
PHOTO: James Tolmie
Controlled-traffic farming (CTF) is generally regarded as the next major advance following the no-tillage development through the 1990s, to generate genuine yield increases and productivity gains in Western Australia’s cropping systems.
In the central wheatbelt researchers, agronomists and growers are seeing crop yield responses of 0.5 to 1 tonne per hectare where CTF is being used in conjunction with deep-ripping on compacted sands.
Results are especially noticeable when growing season rainfall is below average – as was experienced in 2014.
Department of Agriculture and Food, WA (DAFWA) officers Dr Paul Blackwell and Bindi Isbister say global research shows that where CTF is being used to help protect investments in deep-ripping or other mechanical amelioration tactics for compacted soils (such as inversion ploughing, rotary spading, delving and deep working seeding points) the benefits can last for many years.
“Without CTF, the benefits of these tillage systems to alleviate compaction might only last for a season or two,” Dr Blackwell says.
Data collected through GRDC surveys and the Australian Bureau of Statistics in recent years indicates that less than 20 per cent of Australian growers have adopted CTF and its permanent wheel-track system that confines load-bearing machinery to specific areas.
Owners: Colin and Libby Hutchinson
Farm size: 3800 hectares
Average annual rainfall: 325 millimetres
Soil types: hard gravel, grey/red clays, deep sands
Soil pH: 4.5 to 8
Ideal crop rotation: wheat/wheat/barley/canola/legume
2015 program: 2500ha wheat, 650ha canola, 450ha barley
Dr Blackwell says introducing CTF with mechanical deep soil tillage can reduce compaction, improve soil health and cut crop input costs to help offset the capital costs of these systems.
He says research in WA has shown CTF can deliver about 10 per cent higher crop yields, less screenings in cereals and more oil in canola than uncontrolled/conventional traffic systems.
DAFWA-Liebe Group trials at Buntine are also finding wheat yield gains of up to 15 to 42 per cent – depending on the season – are possible from using CTF with deep-ripping to a depth of 35 to 40 centimetres on compacted sands in years with below-average rainfall.
“Unfortunately, in some parts of the wheatbelt in 2014, crop yields were disappointing where it was the first year of deep-ripping,” Ms Isbister says.
“Because of very hot weather, the bigger crop biomass produced at the start of the season from increased nitrogen (N) supply required more water to keep cool and the crop ran short of water to fill grain.
“Such effects should be lessened in coming seasons due to less mineralisation and supply of N from the ripping process.”
Economic analysis by DAFWA shows a $200,000 investment into deep-ripping, spading or inversion ploughing can be paid off within two years if CTF increases crop yield by about 9 per cent.
This is based on 2800ha of wheat grown per annum yielding 2t/ha without CTF at a price of $250/t and 8.5 per cent interest rate for the investment.
Dr Blackwell says it is possible to lift seeding capacity without compromising the CTF system.
“This is done by using higher speeds with wider tyne spacings – and twin row boots – and bigger air carts for a 12-metre-wide seeder, to produce the equivalent efficiency results as an 18m-wide seeder,” he says.
“The common use in WA of larger capacity seeding equipment with high axle loads to improve seeding and harvesting efficiency has very real risks of leading to very deep soil compaction problems.
“Axle loads of about 15t on wet sandy soil can induce root restrictions as deep as 50cm and this may be expensive to rectify in deep sands that need easy crop root access to meet yield potential.”
In a CTF system, all implements have a particular span (or multiple of it) – usually 9m or 12m – and all wheel tracks are confined to specific traffic lanes – usually about 3m.
Deep-tillage equipment can be modified by removing some tynes or spades to only cultivate to depth between the permanent wheel tracks when, or after, a CTF system has been set up.
Deep-ripping compact sands pays off
For the past decade, Yorkrakine growers Colin and Libby Hutchinson have been using controlled-traffic farming (CTF) with three-metre wheel tracks in their no-till system.
In recent years they have started deep-ripping between tramlines in the areas of compacted fine yellow sands that cover about 15 to 20 per cent of their 3800-hectare property.
One-pass deep tillage to a depth of 30 to 35 centimetres, with a 40cm row spacing, is carried out in February and March – on the back of some rainfall and before the seeding program starts. They use an Agrowplow pulled by a front-wheel-assist, mid-sized tractor.
Seeding is done with a deep-blade system (DBS) airseeder bar set up with 25cm spacings and Colin says he gets excellent trifluralin/pre-emergent herbicide coverage.
“All our machinery is matched including the harvester, which runs on 3m wheel spacings with a 12m front; the boomspray, with a 36m boom; and the fertiliser spreader at 24m,” he says.
“For weed-seed management at harvest we have set up conveyor belts on the back of the header to direct weed seed and chaff collected at the front onto the tramlines as they exit.
“The seeding bar and boomspray have extra nozzles set up directly over the tramlines, so
these get double applications of pre and post-emergent herbicides.
“This creates a hostile environment for weeds and is helping us to control our weed numbers. It’s simple: we don’t have to tow a chaff cart, but get another opportunity to destroy weeds.”
Colin says using deep-ripping with CTF on compacted sand areas is paying off, with 10 to 25 per cent higher wheat yields – or up to 1t/ha – in typical seasons or seasons where there is high summer rainfall and minimal finishing rains.
“If we get a tight finish that might produce average wheat yields of 1.5t/ha, we have often reaped 2 to 2.5t/ha on deep-ripped plots because we have eliminated the compacted layer and plants have accessed deep stored soil moisture,” he says.
“The CTF system also allows us to use smaller tractors that are cost-effective, fuel-efficient and versatile for a range of tasks.”
Colin says deep-ripping is a long-term tactic now integral to the way they farm.
0427 102 008,
Watch the video on deep-ripping and CTF for the eastern wheatbelt.
Dr Paul Blackwell, DAFWA,
08 9956 8555,