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.
Grower benefits
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.
Fuel savings
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.
Environmental benefits
Environmental benefits are difficult to quantify, but may affect a farm budget. Interestingly, all environmental benefits of CTF usually correspond with economic benefit to the grower.
Less greenhouse gas emission
There can be less fossil fuel consumption by cropping with CTF and therefore less carbon dioxide emission from a farm. Nitrous oxide and methane formation in oxygen deprived waterlogged conditions may be less on a CTF farm with better soil health than a non-CTF farm, if subsoil constraints have been sufficiently rectified. Thus there may be less greenhouse gas emissions from soil on CTF farms, but this has not yet been extensively assessed in Western Australia.
Less nutrient leaching, especially from deep sandy soils
Less subsoil constraint for root growth on sandy soils will enable better interception of leaching nutrients by roots during winter. This may enable some additional fertiliser efficiency to further reduce input costs. The benefit may only be in the vegetative growing season of the crop and so summer leaching or leaching during extreme rain events would not be reduced.
Reduced water erosion risk
Sufficient anchored ground cover is a primary requirement for reduction of water erosion risk by increasing the erosive resistance of the soil surface to overland flow. Overland flow of water is encouraged by poor infiltration. The good condition of CTF soils, if subsoil constraints have been sufficiently rectified, improves infiltration of large rainfalls and can minimise run-off (see 6.5 Surface water control in the CTF technical manual under External Links for more details).
Changing to CTF
Ultimately all machinery wheel tracks should match to confine the wheels of all heavy machinery to permanent traffic lanes, however larger headers, off-set fronts or airseeders wider than 12m can make matching difficult. To make the process of converting to CTF manageable, developing a machinery investment plan to enable changes within the farm budget is recommended. This may be a plan over a few years. Estimated benefits can help plan pay back times of foreseen costs.
Steps to develop a machinery investment plan
- Decide on imperial or metric measurement (this applies to machines and row spacing).
- Select an operating width and match in multiples (multiples of 9m or 12m are most common).
- Match the tracks (for wheels or tracks with more than a 1t load). Work off header size as it is the most limiting. Ensure machines can go to 3m wheel centres
- Choose the type and width of wheel track you want to leave (fuzzy, bare etcetera).
Before getting out the gas axe to modify machinery widths or axles, experience has shown it is better to measure twice and cut once! In particular, make sure you check the actual cutting width of the header and set the bar width accordingly to avoid leaving unharvested rows of crop.
Components of a CTF system
Guidance systems
CTF needs accurate and repeatable guidance to be able to return to the permanent wheel tracks every time. Global Navigation Satelite System (GNSS) Real-Time Kinematic (RTK) 2cm guidance provides this and is the recommended option. It is likely that proprietary equipment (where one brand is not compatible with another brand) will decline and this will further benefit the industry. In addition, service from Continuous Operation Reference Stations (CORS) Networks and other networks are widely available and this reduces the capital investment. High-quality guidance delivers autosteer, which provides accuracy and reduces driver fatigue. Generally the bigger the cropping area, the greater the savings from preventing overlap by using electronic guidance. Growers with programs greater than 1500ha and input costs of about $100/ha have made savings of about 10% by using an accurate electronic guidance system. This goes a long way towards rapidly recovering the cost of the system. Many WA grain growers no have electronic guidance systems (GPS) and are well positioned to move to CTF. Some growers still chose to use mechanical guidance systems and centre guide row systems in the crop.
Machinery matching
Ideally, all machinery tracks and widths should match, but large grain harvesters with wide wheel tracks, offset harvester fronts and air seeder bars wider than 12m can make matching difficult, often due to the minimum distance of spreading straw or fertiliser. As moist soil is the most easily compacted, spraying and seeding equipment is the most important machinery to match. If you have lots of easily compacted sandplain soil or tend to have wet harvests, serious consideration should be given to incorporate the harvester in the CTF system.
Following is a list of convenient harvester widths, along with the seeder and sprayer widths to which they match. Odd matching ratios of sprayer to seeder (3:1) allow neater paddock edge matching. Even ratios (2:1) need overlap runs at the edge or an extra set of permanent wheel tracks in the wings of very wide seeders.
- Harvester widths: 9m, 10.5m, 12m, 13.5m
- Seeder widths: 9m, 12m, 18m, 21m, 24m
- Sprayer widths: 18m, 21m, 24m, 27m, 36m
However, machinery changes can be expensive, depending on what is already owned. A machinery plan outlining wheel track and implement width is needed. Machinery can then be changed over as part of the farms usual machinery replacement strategy. This may take 5-10 years to have a fully matched system. Eventually there can be less machinery and possibly smaller tractors due to better traction and lower draft requirement.
Many growers have been using partial CTF where the header or some spreading operations or a contract SP sprayer do not fit the whole system. Such partial options still provide some benefits and may be more cost effective for some environments and farm budgets. It is important to review the plan as time goes on to optimise profitability and sustainability.
Why match in the grain harvester?
There are several reasons why matching the harvester into a tramline system is a good idea.
- Harvesters and chaser bins are the heaviest equipment on most farms and cause soil compaction during wet harvests or where soil is moist from shallow water tables. This compaction can be severe enough to remain for many seasons.
- Harvesters will thresh and separate grain more efficiently when large amounts of power are not being used for traction, especially when harvesting on recently deep ripped sand.
- On-ground guidance from spraying tramlines can be confused by wheel tracks from harvest that do not match the tramlines for the other operations.
- There may be integrated weed control options (weed seeds and chaff from harvesters dumped on tramlines), which could be more efficient than chaff carts.
- Full matching of the cropping machinery allows best soil improvement for long term benefits and possible savings in fertiliser requirement.
If you are planning to fit the harvester in, then it is best to base the widths and tracks of the whole system on the harvester because the harvester can be the most expensive piece of equipment to modify. Harvesters with 11m fronts are commonly offset and cause difficulties for matching into 'up-and-back' operations (not such a problem for round-and-round operations), however up to 14m centred belt harvester fronts are now available. If matching the harvester initially requires substantial modifications it is possible to start with matching the seeding and spraying equipment and includes the harvester later. Controlled traffic operators in Queensland who have been in CTF for up to five years are finding that after initially matching only the spraying and seeding equipment they now wish to include the harvester. To accommodate this they are modifying their equipment to 3m tracks.
Tramline design
Traditionally tramlines have been left bare. However, due to concerns with herbicide resistance, gaps in the crop and potential erosion on non-wetting sands (particularly in Western Australia), tramlines are best sown with crop, but with short points or discs to retain firm running.
Layout planning
Whole-farm planning is important when introducing new technologies such as CTF into your system, as a change in paddock layout is often required to utilise the effectiveness of the new technology.
Useful tools for planning layouts include aerial photographs, farm maps, topographic and soil type maps, even yield maps and of course, knowledge of the farm. CTF is compatible with precision agriculture (PA) technologies, such as variable rate technology (VRT). Some changes may take more than one season to put into practice but it is helpful to have a plan for the future. If in doubt about layout contact a professional consultant, as layout mistakes may cause severe erosion damage and are often expensive to remedy.
Design of the most efficient layout considers:
- Length of run
- Access roads
- Tramline orientation
- Surface water control
In high-rainfall areas, all wheel tracks should drain down to a safe disposal area. This allows water erosion to be managed by preventing any flow concentration so wheel tracks do not erode. Waterlogging can also be managed with raised bed layouts in the high-rainfall zone. In practice, there will be low areas in most fields which require drainage.
Experience in Western Australia of water erosion in CTF systems
Source: (Lemon 2006)
The heavy rain in early January 2006 provided a good opportunity to observe the stability of wheel tracks and raised bed drains on sloping land in Western Australia.
Interviews with several growers indicated that erosion had been minimal in parallel cropping systems running down slope. Comparisons with pasture paddocks and previous working patterns indicated that erosion could even been less in down slope working patterns.
The main problems were where water flows concentrated before finding a down hill wheel track or furrow, such as water running out of a reserve onto the paddock or a flat area within a CTF paddock where water moved across working runs prior to finding a sloping wheel track.
Other observations included:
- Erosion was worse on tracks within paddocks than on the wheel tracks
- Cereal stubbles provided more protection than pea stubbles
- Sown wheel tracks and furrows offered more protection than bare lines
- Older raised beds were more stable than newly renovated beds/furrows
- Erosion was a bit worse on wheel tracks on loamy and clay soils compared to sandy soil.
The rationale that many small furrows carrying their own water causes less erosion than a few large depressions carrying accumulated water from larger areas seems to have ‘held water’ in the 2006 extreme rainfall event.
Agronomic opportunities
Establishment of permanent wheel tracks combined with use of a sufficiently accurate guidance system can provide opportunities for in-crop agronomy and soil management without causing unwanted mechanical damage to crops or soil compaction.
Opportunities include:
- Inter-row sowing which has shown to improve seeder performance, reduce potential for root disease and also assist crops such as lentils ‘climb’ the wheat stubble rows to facilitate harvest.
- Close to or on-row sowing to enable access to moist soil in water repellent areas.
- Inter-row shield spraying or mechanical weed control, with care to avoid development of herbicide resistance.
- Band spraying directly over the crop row, to reduce chemical costs.
- Relay planting (planting a new crop or pasture into an existing one before harvest). Banded application of lime, manure, fertiliser or other products.
- Directing chaff and weed seeds onto the wheel tracks for easier management.
- A more compatible system of cropping for in-paddock large scale trials than with machinery that has poor matching of widths and no control of cropping traffic.
Costs
The cost of a transition to CTF varies from farm to farm, depending on what equipment is already on hand. Following is a guide to the cost of upgrading to a CTF system:
Tractor: Front-wheel axle; new cotton reels $3600. Trailed sprayer: axle conversion $3000. Air cart; axle conversion $0-3000. Harvester: Auger extension $1600-2000. Chaser bin extension $16 000. Total base cost: $24 200-27 600. If GNSS 2cm RTK is required + $18 000. Total cost: $42 200-45 600.
It is not always possible to make these changes in one season, so many farms are developing a CTF machinery investment plan in line with their usual machinery change over schedule. In some instances this has meant it has taken a period of 6-7 years to develop a fully matched system.
Challenges
CTF involves a shift in mind-set to a priority of soil health and change in machinery and farm layout that are key components of farm operations. Thus there can be some challenges to consider such as:
- Seeding and harvesting capacity, how to accommodate size and capacity increases for more efficient operations, yet maintain a CTF system. Increased seeding speed and loading capacity can help increase seeding capacity without increase of seeder width.
- High cost of changes in some cases (depending on current machinery and changeover preferences).
- Spreading widths (especially lime and straw), 9m may be the maximum width of spreading of limesand and 12m the maximum width of spreading of straw.
- Burned windrows leading to uneven distribution of nutrients. Swath movement, chaff removal or harvester repositioning in dry harvests soil conditions may be possible solutions.
- Wheel track sinkage and erosion. Use of alternative (dry) tramlines of wing tramlines fro SP sprayers may help, as well as wheeltrack renovators to refill rutted tramlines.
- Staff and consultant training to stay driving on the wheel tracks. This is gradually improved with more education and understanding.
- Guidance compatibility between brands and drift between seasons; this needs careful attention when selecting guidance systems.