The controlled-traffic farming (CTF) maxim is simple: dont drive where you intend to grow crops. Otherwise, the resulting soil compaction hinders rooting depth, rainfall infiltration and yield.

Instead, the CTF approach is to drive all machinery on permanent, narrow wheel tracks by matching all axles to a single track width and making all machines work in multiples of that width.

The goal is to reduce the paddock area compacted by machinery from 40 to 70 per cent down to 10 to 15 per cent.

In February 2019, CTF practitioners and experts gathered at the Third International Controlled-Traffic Farming Conference, in Ballarat, Victoria, to discuss innovations, cost and benefits. The conference was hosted by the Australian Controlled-Traffic Farming Association (ACTFA) and sponsored by GRDC investment.

While speakers generally agreed that implementing CTF can pose challenges, their main message was not a litany of difficulties, but enthusiasm for how to minimise compaction. Manifestly, this is a farming practice that garners exceptional devotion.

Growers reported that by avoiding compaction, soils retain their air-filled porosity. This allows water to better infiltrate soils and remain there, allowing for higher yields, including in tighter seasons.

Additional benefits include lower fertiliser and fuel costs. However, it is the water-management benefits that cause practitioners to identify themselves as 'moisture farmers'.

Among the key CTF benefits reported by growers who addressed the conference were:

• Higher-than-district-average crop yields
• Greater resilience to both water scarcity and waterlogging (when combined with raised beds)
• Improved soil biology (including indications of disease suppression)
• Higher farm selling prices
• Less nitrogen wasted to the atmosphere as nitrogen or nitrous oxide gas
• Compatibility with high-productivity cropping techniques, particularly raised beds (the Canadian concept of 'fence row farming' and inter-cropping).

Growers who have made the switch to CTF described a journey that involved really getting to know their soils, mapping paddock topography right down to how rainfall moves and drains across a paddock and the big CTF item, rethinking farm machinery.

Horsepower

With a CTF system, bigger machinery is not necessarily better or more efficient. Moisture farmers are downsizing their tractors and looking forward to a future that includes small, roboticised machinery that can autonomously work around the clock on narrow permanent wheel tracks.

ACTFA chair Chris Bluett spoke to GroundCover™ and explained that with CTF the two things that happen that reduce the need for horsepower and, concurrently, fuel are:

• Permanent tracks reduce rolling resistance, making it easier to run machinery
• Aerated, non-compacted soil reduces the draft required to pull a seeder through the soil.

He advises drawing up a plan for a targeted equipment replacement program that fits into the time frame of the farms existing program.

"Decide on your CTF dimensions in advance, say three-metre track width, 9m seeder, 27m sprayer, or whatever fits your farm business scale," Mr Bluett says.

"Then make quite sure that every replacement equipment item fits in with that plan."

In many cases, costs can be saved and the changeover accelerated by manually adapting existing machinery, such as chaser bin axles and seeder bars, to match the selected track width and its multiples.

However, Mr Bluett adds that research findings have highlighted one important CTF caveat: not all soil types will automatically remediate from compaction upon adoption of CTF.

Decide on your CTF dimensions in advance, say three-metre track width, 9m seeder, 27m sprayer, or whatever fits your farm business scale.

A calculator to help make CTF machinery investment decisions is being developed, with GRDC investment, by Dr Bindi Isbister and Dr Wayne Parker, of WAs Department of Primary Industries and Regional Development at Geraldton.

Both spoke at the CTF conference and invited growers to try the software and provide feedback.

Soil type caveat

Mr Bluett says there is experimental evidence showing that soils with quite high clay content soils that shrink and swell as they dry out and wet again will self-repair under CTF systems.

"Soils in the Wimmera, Victoria, are a classic case," he says.

"If you remove the compaction from these high-clay-content soils, they will pretty much sort themselves out fairly quickly, over a reasonable number of years, and will continue to improve on their own."

Soils low in clay content, however, tend not to self-repair. The sandy soils in Victoria's Mallee and in Western Australia fall into this non-repairing category.

The solution, then, is to first remediate the soils by doing something 'fairly drastic'. Typically, this involves deep ripping down to 450 millimetres; and deeper if possible.

"There are people farming WA sands that are trying ripping down to 800mm, which is a massive thing to do," Mr Bluett says.

"It sounds drastic and expensive and it is, but if you do that, and also adopt CTF, then you only need to do it once."

Without CTF, you will lose the benefit of the investment even if compaction is subsequently limited to 45 per cent of the paddock area. We need to get down to a minimum of 15 per cent.

Wheel traffic impacts were illustrated by Rachel Hinkley, of Hinkley Farming, in Derrinallum, Victoria, where a contractor's boom on their controlled-trafficked raised beds reduced yield from 10 to seven tonnes per hectare in the affected areas.

"This yield loss reiterated the importance of minimising tracks in a paddock," Rachel says.

More information: Chris Bluett, chris.bluett@hrzconsulting.com