Controlled TrafďŹ c Farming Adoption Guidelines for the Vegetable Industry
What is Controlled Trafﬁc Farming? Controlled trafﬁc farming (CTF) relies on integrating machinery so all ﬁeld trafﬁc travels on the smallest number and area of permanent trafﬁc lanes. It is about using machinery in an organised and precise way to minimise the area of soil damaged by compaction and to increase productivity. Photo: Controlled trafﬁc requires a standard track width so equipment straddles the crop bed. This may require a change in harvest technology, such as this twin row potato harvester and chaser bin.
Why bother with CTF? CTF provides two distinct soil conditions in the ﬁeld – compacted trafﬁc lanes for improved trafﬁc operation and a friable zone for improved crop growth. CTF removes the variability in soil conditions due to trafﬁc compaction. The potential beneﬁts are numerous: • Reduced fuel use and tractor time • Smaller tractors and fewer, lighter tillage implements • Higher yield • Improved timeliness, allowing more effective crop management and opportunity cropping • Improved opportunities for increased retention of crop residues, use of cover crops and inter-row sowing • Improved inﬁltration, water holding capacity, drainage, aeration and soil porosity, with the potential to reduce water use and soil borne diseases • Reduced run-off and erosion Controlling trafﬁc has an immediate inﬂuence on soil structure. There are clear differences in run off from controlled trafﬁc (top) and conventional trafﬁc (bottom) areas of the same paddock after heavy rain following potato harvest.
• Improved soil health • Reduced nitrous oxide emissions • Fewer clods in root crop harvest Widespread experience in various industries shows yield increases of 10 – 20%, fuel reductions of 50 – 70% and improvements in water and fertiliser use efﬁciency. Early experiences in the vegetable industry are very encouraging, although not all beneﬁts have been observed to date. Adoption of CTF provides opportunities to change tillage practices. At present, tillage operations are used to: • repair soil damage caused by trafﬁc • prepare seed beds • manage crop residues • control weeds
Over time, the need for compaction management will diminish, leading to fewer tillage operations and allowing alternative methods of residue management and seed bed preparation.
What do you need and what do you need to do? Interest and commitment First and foremost, you need to decide if CTF is a change you want to pursue. What is your ‘driver’? – lower tillage costs, better soil health, greater productivity? Changing to CTF can be challenging when growing a number of different crops with different machinery requirements, but those who are making the change are seeing the beneﬁts. The most important factors you can bring to the change are commitment, consistency and a willingness to look for reasons to make it work. Virtually no machine you buy “off-the-shelf” will be designed with CTF in mind, so be prepared to invest in modiﬁcations. CTF is an investment in the long term, with the potential to deliver signiﬁcant beneﬁts.
The most important factors you can bring to the change are commitment, consistency and a willingness to look for reasons to make it work.
Think and plan The basic concepts of CTF are very simple; implementation is slightly more complex. Very few people have the resources to start afresh with new equipment, infrastructure and a new farm layout. With careful planning, CTF can be put in place in a number of steps. A plan is essential – how do you want your farming operation to look in the future? Take time to think through the changes required and how to integrate them into your operation. Consider these key points: • Review your cropping rotation and crop establishment systems. Can you make the transition easier by growing fewer crops and still have a good rotation and make a proﬁt? • Decide what machines you will need with CTF. Measure these to see what ﬁts together and what needs to be replaced or modiﬁed. • When is the best time in the rotation to start? What crop gives you the best lead-in? • Farm layout is essential for effective CTF operation. Surface drainage and paddock orientation may need some special attention. • Plan a long term machinery replacement schedule with CTF in mind. In this way, your collection of CTF compatible machinery will gradually increase over time. • Find others who are interested or have already started. Seek out alternative viewpoints and learn from the experiences of others – someone else may have already solved your problem.
Improved soil structure can lead to greater root exploration, as shown with these onions from conventional trafﬁc (left) and controlled trafﬁc (right) areas in the same paddock.
What are the components of CTF? The key components of CTF can be grouped into three areas: 1. Technology and machinery 2. Farm layout 3. Soil management.
1. Technology and machinery Guidance Real Time Kinematic (RTK) 2 cm satellite guidance and repeatable positioning is required for accurate, precise and repeatable CTF operation. The base station needs to be in a ﬁxed location (or able to be reliably returned to a ﬁxed location). A CORS network2 will provide access to readily available correction signals from ﬁxed stations, or you may be able to access signal from a company or community owned base station. If the RTK correction signal is being delivered by a standard base station over radio, reception is effectively limited to line of sight although it can be better in ideal conditions. Ensure the base station is located with a clear view of the sky and the radio aerial is clear of obstructions. Signal reliability will reduce if the base or radio aerial is surrounded by thick trees or the base is close to a large metal object, such as a shed. Even a garden shed can halve the signal range if it is between the base and the rover on the tractor. You may need a mobile repeater to cover areas with poor reception, such as valleys. Reliable 2 cm accuracy is limited to a distance of about 10 km from the base. Beyond this, the error increases by about 1 mm per km and reception reliability decreases, although operation up to 30 km from the base is possible – just be aware of the reduction in accuracy. If purchasing a guidance system, choose one that provides access to multiple Global Navigation Satellite Systems (e.g. GPS, GLONASS, Galileo) to improve your signal reliability. If you don’t have guidance, or believe you can’t justify the cost, access the beneﬁts of the technology by using a contractor who understands and works to the principles of CTF. Remember, CTF is much more than guidance. Machinery integration The integration of track width, implement width and tyre selection is at the mechanical heart of CTF. In an ideal world, the track widths of all wheeled equipment would be the same, equipment working widths would be a multiple of the track width, and tyres would be the narrowest possible within the constraints of load capacity and contact pressures. It is not an ideal world, so compromise may be required, at least at the current stage of CTF development in the vegetable industry. Track width – wider track widths are preferred as they minimise the area of land devoted to wheel tracks. Current vegetable industry tractor track width conﬁgurations vary from 1.6 – 2.1 m, with potatoes being the dominant crop on narrower spacing. A range of fresh market crops (including potatoes) are being grown on 2 m systems in Tasmania. Track width standardisation is the key industry-level issue to address in implementation of CTF. Your choice of track width may be determined by what crops you are growing for which company. Apart from fewer passes in the paddock and improved tractor stability, a 2 m or 2.5 m track width has the advantage of being suited to a number of fresh market crops and it is easy to achieve on many tractors without major modiﬁcation.
1 RTK – Real Time Kinematic – satellite guidance system that obtains a correction signal from a nearby ground-base reference station in order to provide 2 cm accuracy. 2 CORS network – a network of Continuously Operating Reference Stations which operate 24/7 to provide an accurate and reliable correction signal for RTK guidance over the area covered by the network.
Equipment working width – think in terms of bed widths when selecting tillage, seeding or spraying equipment. This is not to suggest all crops are grown on raised beds – the “bed” is the cropping zone between the compacted wheel tracks, and may or may not be raised, depending on need. Equipment working width should be a whole number multiple of the track width – e.g. for a 2 m track width, equipment should be 2, 4, 6 etc metres wide. Two points worth noting when selecting equipment: • If the equipment covers an odd number of beds (1, 3, 5 etc) it may be possible for the actual working width to be slightly narrower than the nominal width, depending on whether it is necessary to include the wheel tracks on the outer edge of the working bout – e.g. 3 x 2 m beds could be cultivated with an implement with a working width of about 5.6 m, but extra width may be required for track maintenance tools at the outer working edges. • If the equipment covers an even number of beds (2, 4, 6 etc) with one bed under the tractor, the working pass will ﬁnish half way across a bed on either side. The width of a tined implement could be narrower than the nominal width by half the tine spacing on each side. A rotary implement will need to be marginally wider than the nominal width to allow for a uniform surface ﬁnish at the join of successive passes. The other issue to consider for passes that ﬁnish mid-bed is how to manage the half bed at the edge of the paddock. Tyre selection – narrower tyres help minimise the area devoted to wheel tracks. As machinery gets larger, wider tyres have become common in an effort to reduce soil compaction and improve load capacity and traction. Under a fully integrated CTF system, equipment can be lighter, draft requirements may reduce by 50% or more, and traction conditions will be much improved because of the compacted tracks. While CTF is still a developing practice, use the narrowest radial tyres possible to avoid the need for high inﬂation pressures. Harvester integration – for all the beneﬁts of a standard tractor track width and compatible implement widths, the major mechanical challenge in the vegetable industry is trying to match harvest equipment. This is an issue on three counts: • many harvesters have incompatible track and/or working widths • many harvesters are not suitable for modiﬁcation • many harvesters are operated by contractors, who may have more to invest and less to gain from a change to CTF. This makes full equipment integration particularly challenging in the vegetable industry and in some cases the only option is to consider alternative technologies. For example, centre-pull twin row potato harvesters are much easier to modify for CTF than single row harvesters. The key consideration in any modiﬁcation is to maintain load capacity and stability on slopes. There will always be harvesters which are incompatible (e.g. pea viners) regardless of other decisions about track widths etc. In addition, grain harvesters with 3 m track widths create another challenge for full integration, although there are options to manage the mis-match between grain and vegetable equipment (see below – Integrating vegetable and grain operations).
2. Farm layout Controlled Trafﬁc Farming layouts are best done up and down slope. Machine tracking is easier up and down, rather than across, slope and surface run off is less likely to cause erosion across the beds. Round and round operations have no place in CTF. Operating up and down slope is normal practice in many vegetable production areas. However, it is common for some parts of the paddock to be on a side slope. This may require extra attention for accurate machine tracking and guidance (see below – Operating and maintaining a CTF system – Tractor stability and implement tracking). Surface water management in CTF systems is important for two reasons: • Run-off and erosion control, particularly for steep slopes • Wheel track drainage, particularly on low slopes, or where complex slopes create low lying areas.
Surface water management on slopes may require extra infrastructure. Erosion risk in the compacted wheel tracks is a common concern, although limited experience so far suggests improved inﬁltration in the crop bed means less water in the wheel tracks. Upslope diversion drains to prevent run-on, and down slope drains to collect run-off, are key considerations of good layout. These should take water away as fast as possible and be broad-based and grassed for ease of trafﬁc movement. They may be incorporated into paddock headlands. Complex slopes often have run-off collection points or cross paddock drainage lines. These should be drained using grassed waterways, correctly mapped and designed to minimise erosion risk. Alternatively, if drainage lines are not likely to carry a large amount of water, install rip-mulch lines on the contour each cropping season. Most guidance systems provide contour tracking options. Flat or very low slope paddocks present particular challenges. Accurate mapping (using data from your guidance system) is important for designing a layout that is efﬁcient for CTF and surface water management. Laser grading the base of the wheel track may be an option. The bed height may vary a little, but if it is an option, it is much cheaper than grading the entire paddock. Daily harvest pressures for fresh produce can be a challenge in any farming system, including CTF. You don’t always have the luxury of waiting for tracks to dry, but if they are properly drained they will regain their strength faster.
3. Soil management Controlled trafﬁc leads to changes in the condition of the cropping soil and therefore also in the soil management practices – less tillage, lighter tillage, perhaps no tillage in some situations. This will inevitably inﬂuence the machinery you will need. There are many different options to be explored – what is best for your situation will be found through experience.
Improved soil structure resulting from controlled trafﬁc can reduce the tillage required for seedbed preparation. Planting potatoes into uncultivated soil is possible in some situations.
Operating and maintaining a CTF system Mapping and record keeping When establishing CTF, it is essential to record and save paddock maps with the A-B lines. The best guidance technology in the world is pointless if you don’t keep paddock maps so you can return to the same wheel track locations every time. Map, record and save and then use the same map next time. Likewise, your base station must be in a permanent, or at least accurately relocatable, position. Trafﬁc movements In the early days of CTF implementation, it is important to accept that not all machinery wheels will be where you want them. Errors in tracking and mismatched equipment dimensions are just two reasons why wheel tracks might occur in places you would prefer they didn’t. Those issues will be overcome with time and experience. However, there are some wheel tracks that have no place in a CTF system. These include: Trucks – there is no place on the paddock for trucks other than on a headland or loading bay. Truck tyre pressures and conﬁgurations are made for roads and that is where they should stay. U-turns in the paddock – part of developing consistency around CTF operations is to think in terms of end-to-end travel in the paddock, so avoid mid-paddock U-turns or pull outs. This may not be so important in a Seasonal CTF harvest situation (see below), but developing the habit helps develop the consistency of operation required for CTF. If crop rows are too long for efﬁcient operations over the full length of the paddock, have an access headland mid-way which might also aid drainage. Random, unnecessary vehicle movements – general farm trafﬁc, such as utes and other vehicles, should be kept off the CTF area. Once again, this may not be so important after a Seasonal CTF harvest but should be avoided at all other times. Field operations and maintenance Over time, CTF will make ﬁeld operations easier if you are consistent. Tracks – keeping machinery tyres off the cropping soil means less effort to prepare it for growing a crop. As CTF evolves towards a fully integrated system, the focus in ﬁeld operations is likely to shift away from seed bed tillage and towards track maintenance. Although proper tyre selection can minimise track damage, it is likely there will be times when there is no choice but to trafﬁc when the tracks are very wet. This is where drainage is important (see Farm Layout). You need to be prepared to conduct repair operations at some stage. This may involve cleaning out the track, or maybe bringing soil back onto the wheel track to compensate for rutting. Part of track maintenance may be the inclusion of targeted tillage along the edge of the crop zone to remove compaction from inaccurate tracking, mismatched machines or wide tyres. Tractor stability and implement tracking – maintaining tractor and implement stability on compacted tracks can be a challenge, particularly on side slopes. It is normal to keep the wheel tracks as narrow as possible to reduce the area of tracks. Driving on narrow, compacted tracks can be difﬁcult even in dry conditions. Options to overcome this include stabilising discs which may be ﬁxed, or steered with an implement guidance system. This issue is even more important when tracks are wet. Recent experience has shown that working the surface of the wheel tracks to a depth of about 10 cm can help with tractor tracking on subsequent passes. This loses some of the advantages of a fully compacted track but makes tracking easier. Tillage – all tillage operations need to be in the same direction as the wheel tracks. Cross-ripping is incompatible with CTF and as soil improves should be unnecessary.
Where to start and how far can you go? There are many challenges to implementing a fully integrated CTF system in vegetable production. The greater the diversity of crops and contractors on your farm, the more difﬁcult the change. A starting point for adoption is Seasonal CTF, although it is important to keep your long term goal of fully integrated CTF in mind.
Seasonal CTF Seasonal CTF keeps all tillage and crop management operations on permanently located wheel tracks but accepts that current vegetable harvest equipment is incompatible with maintaining the CTF operation through the harvest process. Consequently, the impacts of harvest trafﬁc need to be repaired with post-harvest tillage. With guidance and appropriate matching of tractor track and equipment width this can be done on the same wheel track locations each season. The process is illustrated in the diagram below showing a normal cropping cycle.
Controlled trafﬁc Seed bed preparation, seeding, crop management
Primary and secondary tillage
Initial set up Given the current constraints of harvester integration, a deep ripping operation after a heavily trafﬁcked vegetable harvest is probably as good a time as any to start out with CTF. This should only be done if the conditions are right for loosening – i.e. soil moisture content at the depth of ripping will initiate cracking rather than smearing. There are two ways to approach this deep ripping operation: • Ripping and cross-ripping will fully remove harvest trafﬁc compaction. The CTF wheel tracks are then set up when the next operation is performed over the top of the loosened soil. It is best to install the tracks when the soil is moist, but not too wet, as this will give a good level of compaction in the wheel track. • Ripping only in the direction of the proposed wheel tracks, but leaving the wheel tracks unripped, or maybe ripped at a shallower depth. In this case, the ripper tines in line with the tractor tyres can be removed or shortened so the compacted soil from harvest remains as the basis for the permanent wheel tracks. Your choice of approach may be inﬂuenced by the operations required to prepare a seedbed and establish the next crop. For example, if ripping only in the direction of the wheel tracks would cause tracking problems for subsequent operations, cross-ripping would be the preferred approach.
Integrating vegetable and grain operations Even if you could establish a fully integrated vegetable CTF system with compatible equipment, it is unlikely to integrate perfectly with grain operations. Grain harvesters have a track width of 3 m, or close to it, as do a number of poppy harvesters. Although 3 m track widths are used in parts of Europe, there doesnâ€™t seem to be much interest in that option for Tasmanian vegetable operations for a number of reasons. A way of integrating vegetable and grain systems is needed. The system illustrated below uses a 2 m track width for vegetables and a 3 m track width for grain harvest. The grain harvester tracks outside the tractor wheel tracks. The resulting tracked area in this case is 36%. The harvester wheel tracks can be loosened by targeted tillage before returning to vegetable cropping. The same principles can be applied to other dimensions.
6 m implement
6 m implement
6 m implement
18 m spray boom
6 m harvester 3m
6 m harvester 3m
6 m harvester
The cutting front on the grain harvester should be marginally wider (about 20 cm) than the nominal working width to allow for crops that lodge across the direction of travel. Another consideration for grain harvest is straw management. If straw is not baled and removed it should be chopped and spread as evenly as possible across the cutting width. This will allow for easier residue management in subsequent tillage operations or may allow easier adoption of zero-till if appropriate.
Conclusion The beneﬁts of CTF are numerous and they all depend on the changes that occur in the soil by removing trafﬁc from the cropping zone and concentrating it in the permanent wheel tracks. This is what provides the numerous beneﬁcial soil structure changes and the improved machine performance. In the end, the key considerations are: will it provide a bigger proﬁt margin and is it practical? There is limited vegetable industry experience to provide deﬁnitive answers to these questions at present. There is good evidence that fuel costs and time costs will decrease. Experience in other industries has shown increased yields and cropping frequency, decreased fertiliser use and more efﬁcient water use. Over time, it should be possible to reduce machinery inventory. On the expense side is the cost of modiﬁcation or replacement of machinery. Each situation will be different, based on how much equipment needs to be modiﬁed, the size of operation, the use of contractors etc. Experience in many different industries and situations suggests the savings in equipment inventory are generally greater than the costs of conversion. One thing is certain – while input costs continue to rise, CTF has great potential to reduce inputs and increase productivity. One other thing is also certain – CTF will be adapted and adopted in the vegetable industry. While there is still a lot to learn, the potential rewards will drive the change and those who embrace the change will be the leaders in production efﬁciency.
TIA is a joint venture of UTAS and the Tasmanian Government
This project is supported by Cradle Coast NRM, through funding from the Australian Government’s Caring for our Country and the Tasmanian Institute of Agriculture. Acknowledgement is given to W C T Chamen (CTF Europe Ltd.) for the illustration of integrating mis-matched equipment track widths.
Controlled Traffic Farming Adoption Guidelines for the Vegetable Industry 2013