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Australian growers halt worsening of soil compaction with CTF

Growers in Australia have basically halted the worsening of soil compaction with Controlled Traffic Farming, says Dr Rohan Rainbow, Managing Director of Crop Protection Australia. “It’s the dominant best practice farming system in this country.”

The issues with soil compaction have been known in Australia for well over 30 years, Dr Rainbow explains. “Particularly in the last 15 years producers in this country have actually adopted high rates of Controlled Traffic Farming (CTF). The rate of adoption for no-till practices in broadacre are over 85%. Almost half of those producers are practising some degree of CTF.”

Improvement in crop growth and yield

Dr Rainbow points out that CTF is generally recognised for its production and efficiency benefits. “The trafficability is higher. When it is wet, it is not such a big issue to get over the ground. But also the impact of compaction, the improvement in crop growth and yield are well understood here. This is primarily why we have got high rates of adoption.”

A lot of Australian soils are not of a high quality, Dr Rainbow says. “There are many loamy sands overlaying clay. And the higher the sand content in these loams, the worse the issues with soil compaction are. In a clay soil with shrinkage and contraction, and wet and dry periods, the hard pan soils can actually break up again with time. But if you have a higher sand content, you don’t have that phenomena. Essentially it just gets harder and harder.”

Significant decline in roots growth

When soil compaction gets above 2.5 megapascals of penetration resistance, growers face a significant decline in roots growth. “This is a critical level”, Dr Rainbow says. “There is a simple test I have used many times at field days. You get a 3.25 mm high carbon welding rod with the flux removed. If you press the rod with your open palm all the way into the soil you are below this critical threshold. However if it hurts too much to press down, you are likely to be above 2.5 megapascal soil resistance. You can’t easily see compaction, but you can feel compaction.”

According to the Australian wide initiative ‘Soilquality’ CTF is the best way to minimise compaction and protect investment in soil amelioration, such as deep ripping which can be expensive. A big advantage are the lower energy requirements for seedbed preparation, including less rolling resistance when driving over the compact traffic lanes.

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CTF is the best way to minimise compaction and protect investment in soil amelioration, such as deep ripping which can be expensive. A big advantage are the lower energy requirements for seedbed preparation. - Photo: Rohan Rainbow
CTF is the best way to minimise compaction and protect investment in soil amelioration, such as deep ripping which can be expensive. A big advantage are the lower energy requirements for seedbed preparation. - Photo: Rohan Rainbow

Improved water holding capacity

Improved soil structure through reduced compaction results also in improved water holding capacity. There is improved efficiency of some soil immobile nutrients by placing fertilisers closer to the plant. The soil is in better condition to provide nutrients to plants. Soil quality emphasises that studies worldwide have shown that uptake of fertiliser improves around 15 %.

Another advantage is the lower tractor capital that is needed. Firm permanent tramlines and softer soil between tramlines improve tractive efficiency reducing average power requirements. And improvements in soil quality through reduced compaction also point to the fact that all these benefits will result in improved crop yields. In crops of lupins there is an advantage of 10%. In wheat crops the advantage is 13% and in canola crops producers gain 11% using CTF.

An added benefit of CTF if removing subsurface or seedbed compaction through deep ripping, is that soil will continue to remain loose and friable for many years after natural settling, as soil is not being trafficked back to its original compacted state.

The Australian Bureau of Statistics estimated a few years ago that 6.7 million hectares, or about one-third of Australia’s total crop area, was operated under a CTF regime, totalling 41% of growers.

High rate of autosteer adoption

Dr Rainbow explains that farmers basically have halted the worsening of soil compaction in Australia with CTF or Tramline Farming. “We have aligned the wheel tracks of our tractors, spray units, harvesters and so on commonly at 3 metre centres, sometimes 4. And there is also a very high rate of autosteer adoption in Australia. The adoption rate is now probably more than 90%. Autosteer makes the control of CTF-systems a lot easier.”

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Dr Rohan Rainbow: "CTF is recognised for its production and efficiency benefits. The trafficability is higher. When it is wet, it is not an issue to get over the ground." - Photo: Rohan Rainbow
Dr Rohan Rainbow: "CTF is recognised for its production and efficiency benefits. The trafficability is higher. When it is wet, it is not an issue to get over the ground." - Photo: Rohan Rainbow

Australia was one of the first countries to develop CTF. “We had the combination of good science and some real practical hands-on engineering”, Dr Rainbow says. “That helped to facilitate the change. It is not easy readjusting all the wheel tracks. Since then all machine companies here – John Deere, Case IH, New Holland and alike – have purposely designed and built tractors for the Australian market. Typically front wheel assist tractors around that 200 to 300 horsepower mark are well suited for CTF.”

Growers were actually able to purchase smaller and more efficient tractors

An important effect of the introduction of CTF in Australia was that farmers were able to reduce the size of their tractors. “Because of the tractive efficiencies the pull of the tillage equipment through the soil became easier because it wasn’t as compact”, Dr Rainbow explains. “There was a saving of 25% to 30% in terms of engine horsepower required to do the same job. Growers were actually able to purchase smaller and more efficient tractors. And just reducing overlap in itself, provided producers with savings of between 8% to 12%.”

Machine autonomy

The positive effects of using CTF on yield production vary on the season and the particular circumstances, Dr Rainbow points out. “It is anywhere between 5% and 15%. It all depends on the soil type, the seasons. But it certainly payed dividend, which explains the high rates of adoption. People adopt things that pay.”

‘Timeliness improved’

David Greig from Tottenham in New South Wales says that it was a challenge to change his mindset to CTF. An early hurdle was teaching staff and contractors to stay on the tramlines. “People often didn’t understand what I was trying to achieve”, David says.
The Grieg’s started with CTF in 2008. Only a new tractor was necessary. They have a farm with winter cropping and sheep. Wheat and canola are grown as cash crops and oats and lupins are grown for grazing and fodder.

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David Greig: "Water infiltration has been improved resulting in more even crops." - Photo: David Greig
David Greig: "Water infiltration has been improved resulting in more even crops." - Photo: David Greig

David believes CTF is providing savings in fuel with firm tracks providing better roll. He is now able to get on to his country much more quickly to spray and with less mess, particularly in wet conditions. Timeliness has improved.
David says his soils have become softer. Water infiltration has been improved resulting in more even crops. “I have noticed more consistency across all soil and crop types. I am now more confident in predicting crop yields based on available stored moisture and in trying new crop varieties.”

Standards for agricultural field machine autonomy

Dr Rainbow thinks there are a lot of extra benefits to be gained in the further development of machine autonomy. He is currently leading, on behalf of Grain Producers Australia, The Tractor and Machinery Association of Australia and the Society for Precision Agriculture Australia an initiative to introduce the world’s first Code of Practice with standards for agricultural field machine autonomy.

According to Dr Rainbow there is a clear need and opportunity for the Australian agricultural industry to develop this Code of Practice. “It will build confidence for commercial investment and will build social confidence in its use. A Code of Practice will also provide a clear argument reducing the need for overly prescriptive regulation. It will help to better support the commercial introduction of autonomous tractors and machinery into Australia.”

Robotics and autonomy

Dr Rainbow expects robotics and autonomy to see high rates of adoption in Australia in the coming years. “We are now setting things up so we can do this commercially”, he says. “But it is such a significant change in practice. It is very important that we get the stewardship of the technology right. At the moment there is no specific legislation covering this in Australia. It is a bit of a blank sheet.”

Autonomy will be the next big step for farmers in broadacre, Dr Rainbow emphasises. “After the high rates of no-till, CTF-systems and autosteer, the next step will be to automate the farming process.”

And the Australian market is ready, Dr Rainbow says. “There are few regulatory barriers for autonomy on-farm, but the Australian government has a principle of reducing red-tape and regulation so a code of practice is an appropriate step forward for agricultural industry. Large scale tractor autonomy seems to be a key priority. Autonomy will also improve stewardship of pesticide application under the code of practice.”

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It can take anywhere from five to 10 years for growers to match their machinery for CTF. - Photo: Rohan Rainbow
It can take anywhere from five to 10 years for growers to match their machinery for CTF. - Photo: Rohan Rainbow

Conversion into CTF should be gradual

According to a publication of the Grains Research & Development Corporation (GRDC) research data has now proven the value of Controlled Traffic Farming (CTF) across a wide range of soil types from Vertosols of southern Queensland to the yellow sands of Western Australia.
Modelling data using the MIDAS program in Western Australia showed an AUS $ 200,000 cost of conversion to CTF which may be paid off in two years, assuming yield increases of about 9%. A study from southern Queensland indicated that a 17 per cent return on capital was achievable from converting to CTF with an AUS $ 137,000 investment, with a payback period of 5.9 years.
“The conversion into CTF should be a gradual process in line with standard machinery replacement strategies. Using a guide such as the ‘machinery income efficiency’ ratio helps determine the value of machinery relative to farm income”, according to the GRDC-publication.
Bigger machinery is not always the most efficient and growers are encouraged to record their actual field efficiency with current gear.
“Assess where inefficiencies are occurring, especially during sowing when most growers (and machinery dealers) look to going wider”, the authors emphasise. “To increase capacity at sowing, consider whether speed can be increased without compromising establishment.“
The authors point out that it can take five to 10 years for growers to fully match their machinery for CTF, taking into account sound financial management to replace machinery when it is due and not any earlier. “Growers should stage their machinery changeover for CTF with an easy first step being the boomspray, followed by the linkage spreader, then eventually the header or seeder subject to machinery replacement schedules and farm income.”
“Consider using a machinery investment plan where all current machinery is listed with its age and when it is due for replacement relative to existing requirements or expansion plans for the future.”

One comment

  • Gerrit Kurstjens

    Well written, the other advantage of autonomous machines is you can cover double the area with the same machine, which can result in half the cost per Ha.
    Beefwood Farms, Moree

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