Another term for controlled traffic farming that has been commonly used is ‘tramline farming’. Controlled traffic farming and tramline farming have been used interchangeably in Australia. Controlled traffic farming is now the more broadly used term world wide for a system with permanent traffic lanes. Tramlining in Europe refers to seasonal wheel tracks that are commonly used for spraying and are usually replaced each year.
Crop yield and quality improvements
Australian research over 20 years has shown CTF can improve grain quality and increase grain yields by 2-16% (10% is a common average after the year of establishment) if there are no other limiting subsoil constraints. These benefits are attractive, but ultimately a new farming system has to produce more profit. A recent estimate of profit from large-scale dryland grain farms is for a modelled Western Australian farm. The average profit from cropped area greater than 1000 hectares (ha) is $47/ha. Roughly half the profit came from improved yield and the other half from improved grain quality; fuel saving is a relatively minor component. Economic modelling has shown doubling of estimated profits of a mixed enterprise farm greater than 2000ha with a range of soil types in the Western Australian central wheatbelt increasing with use of CTF.
Spending less money on fuel is the CTF benefit most growers find as soon as they get their system going. Improved fuel use efficiency comes from machinery running on firm compact wheel tracks with less rolling resistance and wheel slip compared to running on softer soil. 25% reduction in fuel use has been measured in CTF systems with no-till farming in Western Australia. When combined with fertiliser savings from less overlap from guidance, this could translate to 200 tonnes of greenhouse gas avoided for every tonne of improved grain production. Queensland research has shown up to 50% less fuel use when CTF is used on clay soils.
Reduced fertiliser requirement
On CTF farms fertiliser may be used more efficiently (more grain is grown for the same amount of fertiliser per millimetre of growing season rainfall). Alternatively, less fertiliser may be needed to grow the same yield for the same amount of growing season rainfall. This seems to be due to better soil health, which improves increased beneficial microbial nutrient transformations, such as mineralisation of nitrogen and fewer detrimental microbial nutrient transformations, such as denitrification. Better soil health of soils under CTF seems to come from more porous and easily drained soil decreasing the frequency and duration of waterlogging, as well as encouragement of soil macrofauna (worms, ants and termites). CTF and no-till in a low rainfall loam has been found to encourage activity of termites and led to better yield, most likely from nitrogen fixed by nitrogen-fixing bacteria in the termite gut. Abundant termite activity has been observed on well-established CTF farms on sand and loam in the low rainfall north-eastern wheatbelt and abundant earthworm activity has been observed on a well established high rainfall farm on clay soil near Esperance. Detailed studies of soil biology effects of CTF and no-till treatments to a vertisol in south-east Queensland found CTF could increase abundance of earthworms, mites and springtails by 160%, 40% and 40% respectively, compared to wheeled treatments.
The combination of reduced denitrification loss as nitrous oxide and reduced loss of nutrients in run-off, together with reduced leaching and improved soil biological activity, might account for the anecdotal claims of enhanced yields from reduced nutrient input.
Reduced capital cost, depreciation and better use of capital
Firm wheel tracks and soft soil enable better traction and less draft for the same seeding or tillage operation; thus lower horsepower tractors, such as front wheel drive tractors, can be used. Tracked tractors can take advantage of this because they have a higher tractive efficiency than a wheeled tractor, which may need duals or triples to provide the same draft. The lower capital cost of a smaller horsepower tractor will provide benefits of lower depreciation cost and a better fit to other on-farm operations (such as spraying, spreading and pulling chaser bins) than a larger horsepower tractor. This benefit has often been included in CTF farms in eastern Australia and more Western Australian farmers are becoming aware of it and using lower powered tractors.
Protecting investment in deep cultivation
Any tillage system that conserves the permanent wheel tracks can be used in CTF; even full-tillage such as inversion ploughing can allow later restoration of permanent wheel tracks, which is essential if a large investment in deep tillage and soil amelioration is to provide long-term benefit. Where soil types are responsive to amelioration, this will be an additional cost that will add value to a farm CTF system (unless subsoil constraint management has already been planned and CTF will be integrated with it). Initial deep cultivation costs can be relatively easily estimated from known evidence, but the fuel estimates may be reduced for the area of permanent wheel tracks, which may not be treated (for example in modified deep ripping or spading). There are also avoided costs to consider, the longer period before deep cultivation will be needed again, due to less subsurface compaction by traffic. Recultivation may only be required from eventual settlement under wetting and drying and flooding or electrochemical instability and the need for deep incorporation of gypsum. Recent farm observations on some deep sands have found the benefits of deep ripping persisting for at least ten years on a fully matched CTF farm.