- Switching to controlled-traffic farming (CTF) can reduce the compacted area from 40 to 60 per cent to less than 20 per cent
- Nationally, almost 30 per cent of cropped hectares are managed under a CTF system
- The cost of converting to CTF can be very low if machinery is purchased as part of the standard replacement program
The idea of controlled-traffic farming (CTF) systems goes back to the 1850s - when early pioneers considered using permanent tramlines made with railway iron, to handle steam-engine traffic in the field.
However, it really took off with the adoption of no-till farming systems in the 1990s and subsequent increases in machinery scale.
Nationally, almost 30 per cent of cropped hectares are managed under a CTF system - ranging from more than 60 per cent in central Queensland to about five per cent in the South Australian and Victorian Mallee.
These differences reflect local farming systems, with central and southern Queensland and northern New South Wales historically relying on stored soil moisture for winter crops.
Southern systems, including in Western Australia, have traditionally relied on in-season rainfall. However, in recent years, rainfall variability has increased the importance of stored moisture here as well.
Calculating the cost of compaction
Calculations - based on common broadacre machinery sizes - suggest non-CTF systems will traffic and compact from 40 to 60 per cent of paddock area annually, while a good CTF system will traffic less than 20 per cent.
Research shows that any machinery with an axle weight of 10 tonnes or more can cause compaction below 300 millimetres, with most of this compaction occurring in a single pass.
Growers can use the CTF Calculator, developed by Precision Agriculture in conjunction with the WA Department of Primary Industries and Regional Development and GRDC, to determine their own trafficked percentage using current gear and future potential scenarios.
Yield benefits from removing traffic vary, but research from around Australia has shown compaction yield penalties average from 20 to 35 per cent.
While some soils that shrink and swell have the ability to self-repair, many require mechanical amelioration to remove compaction.
Finding uncompacted areas can be a challenge, but one good way of estimating yield penalties is to look at crop performance near non-living paddock obstacles - such as powerlines.
The cost of converting to controlled-traffic farming can be very low if growers work new purchases into the standard machinery replacement program.
Moving to CTF
Converting to CTF can be easy if current machinery is already at complementary widths and the only necessary changes are wheel-spacing modifications to create a fully matching system.
Other enterprises might need operators to replace all current machinery to create a system that works effectively.
Working CTF purchases into a standard machinery replacement program can minimise the cost of moving to CTF and some purchases can be brought forward once the business is close to reaching a full CTF match.
A survey of WA growers found it cost less than $20,000 to move to a CTF system - with changing wheel spacings representing the majority of this cost.
Growers who have converted to CTF almost universally report a reduction in fuel costs, with savings of 15 to 30 per cent not uncommon.
Additional benefits such as better paddock access, better drainage and easy trial layout all contribute to CTF's appeal.
Economic modelling by The University of Western Australia in 2011 estimated that CTF increased income by $31 per hectare through improved yield and quality (based on a wheat yield of 1.2 tonne per hectare and price of $265/t) and reduced input costs (mainly fuel) by about $15/ha.
Across a 1500ha property, the annual profit increase was about $73,000.
Previous research on the Darling Downs in Queensland found an expected profit increase of $87/ha from converting to a CTF system.
Between fuel savings and yield improvements, the economic benefits of CTF are clear.
GRDC Research Code DAQ00194
More information: James Hagan, DAF Queensland, 07 4529 4273, firstname.lastname@example.org