Controlled traffic farming the costs and benefits

Author: | Date: 16 Feb 2016

Background

Controlled traffic farming involves the use of permanent three-metre wheel tracks in order to reduce the negative impacts of soil compaction on rainfall infiltration, rooting depth and eventual crop yield. By matching the widths of farm machinery, wheel traffic is reduced from being 40-70 per cent of the paddock, down to 10-15 per cent. The improvements in soil structure between wheel tracks are particularly beneficial to crops during the critical periods such as establishment and grain fill. Conversely the permanent tracks become more compacted with every machinery pass, which leads to better traction when conditions are wet, improved timeliness getting back onto paddocks after rain and reduced fuel use.

In a CTF system, the working width of each implement is matched to multiple widths of the narrowest implement. For example in a 12m, 3:1 system, a 12m seeder matches a 12m header which is covered by a 36m boomspray and 36m linkage spreader. This equates to 11 per cent of the paddock being covered by wheel traffic in a fully matched 12m system (or 15 per cent in nine metre system).

Illustration of tractor wheel base showing integer multiple of base module.

Figure 1: Chemical applications- integer multiple of base module.

The wheel base of each machine or implement is matched to line up with the header which comes with a fixed axle width of three metres. The header usually forms the basis of a desired working width for CTF systems, being the heaviest machine used in dryland cropping operations. Autosteer using two centimetre  real time kinematic (RTK) guidance is essential for CTF to allow repeatability of all operations on the same tracks.

A standard no-till system operating with RTK guidance, but no CTF, is estimated to traffic approximately 52 per cent of the paddock. This could include a 15m (50ft) seeder, 36m (120ft) boomspray, nine metre (30ft) windrower and chaser bin on 2.2m axle widths not running on tramlines.

There are a number of decisions that need to be made when planning the move into a CTF system, including modifying machinery versus the cost of replacing equipment over time, and which machinery widths would best suit the current and future needs of the business.

The benefits of CTF

Initially developed in Queensland to reduce soil compaction and runoff issues, CTF has now expanded to include a wide range of soil types and farming systems around the world. The original principle is based on a theory that plants grow better in soft soils and wheels traffic better on hard soil. There are a broad range of benefits with CTF which primarily relate to improved soil structure, complementing the gains achieved through no-till and stubble retention practices. These benefits include:

  • Improved timeliness and ease of operations
  • Reduced dust in summer when spraying on permanent tracks
  • Improved trafficability in winter for spraying and spreading
  • Decreased soil bulk density
  • Increased aggregate stability
  • Increased infiltration and visible porosity.

A primary driver for the increased adoption of CTF is the impact on reduced soil compaction and the subsequent impact on crop growth or yield. Changing climatic conditions have seen an increased reliance on subsoil moisture, so that addressing subsoil constraints such as compaction, sodicity or acidity - which limit plant access to the soil moisture profile - is even more critical for grain fill and yield.

Growers are now pushed to complete operations in tighter windows to optimise timing or maximise labour availability. For example, spraying, spreading and harvest are often conducted on wet soils to target ideal crop growth stages or minimise quality downgrades at harvest. In conjunction with the substantial increased weights of farm machinery in recent years (Table 1), causing impacts on soil compaction.

A modern Class 8 header (e.g. John Deere S680) weighs in at 34 tonnes when fully loaded and whilst it can be argued that compaction does not occur at harvest on dry soils, it only takes one wet harvest for deep compaction to last many years. Southern NSW has experienced significant rain events during four of the last five harvests, wetting the soil profile down to 10-20cm in many instances. Due to time and grain quality pressures, many growers are often back harvesting within one to two days after a rain delay. In random traffic systems this would be creating compaction to depth across a large proportion of the property which, depending on soil type, would reduce yield in subsequent crops and be costly to rectify through deep ripping.

Table 1: Weight of common farm machinery in 2016.

Machinery Weight
Bourgault 18m 3320 airseeder bar 18.7t
Bourgault 6700 air cart 11t empty, 30t full
Case Patriot 4430 36m SP boomspray 14.2t empty, 18.7t full
Goldacres 7500L 36m boomspray 5t empty, 12.5t full
John Deere R410 articulated 4WD tractor 18t
John Deere S680 header 34t full
Coolamon Steelworks chaser bin 30 ton 8t dry, 43t full

Impacts on yield

Research data has now proven the value of CTF across a wide range of soil types from Vertosols of southern Queensland to the yellow sands of WA, yet adoption remains low across the clay loam soils of southern and central NSW. This is largely due to limited data for this area, with no research conducted that includes the use of commercial scale machinery for assessing the impact of compaction.

A trial conducted from 2000-2001 on a sodic brown clay (Vertosol) at Grogan, NSW, was monitored under simulated CTF conditions after removal of a pre-existing hard pan by deep ripping. The deep ripped areas were soon re-compacted by wheel traffic the following year. The trafficked area had greatly reduced root growth of both wheat and canola with higher bulk density and soil strength compared to between the wheel tracks. Canola yielded 3.2t/ha between the wheel tracks, but only 1.1t/ha in the compacted zone, in an above average rainfall season on heavy clay soils. There was no difference in wheat yield at 5.3 t/ha versus 5.5t/ha, potentially reflecting the differences between the tap root system of the canola and fibrous roots of the wheat.

A project from 1989 to 1994 on a red chromosol at Roseworthy in South Australia (SA) showed improvements can also occur when CTF is implemented without prior deep ripping. Barley, wheat and faba bean yields increased by 12-17 per cent in five of the six years when wheel traffic was confined to only 10 per cent of the crop area. Soil structure changes resulted in improved soil tilth for seeding and better seed-soil contact in the CTF and no-till treatments. Harder wheel tracks in CTF plots were more trafficable and reduced rain delays for operations.

The adoption of CTF following deep ripping in Western Australia (WA) is gaining momentum, with yield increases at Esperance between 18-46 per cent resulting from deeper rooting depths and access to soil water. Various WA trials suggest that yield penalties from compaction on deep sands can range from 20-47 per cent with duplex soils averaging 22 per cent. The key outcome from the WA trial work has been the importance of removing the compaction layers first, then avoiding re-compaction through the adoption of CTF.

Economics

Modelling data using the MIDAS program in WA showed a $200,000 cost of conversion to CTF which may be paid off in at little as two years, assuming yield increases of about nine per cent. A study from southern Queensland indicated that a 17 per cent return on capital was achievable from converting to CTF with a $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. This is based on total machinery assets divided by farm income averaged over the last four years.

Machinery income efficiency ratio = total machinery assets (clearing sale values)
farm income (past four years)

Target ratios should fall between 0.7 and 1.2, relative to the role machinery plays in the business, with productivity, labour or debt considerations. Use rules of thumb outlined in Table 2 to guide realistic operating timeframes for machinery. The most efficient operators certainly never have the newest or biggest gear - they simply keep it running and well maintained. Serious consideration should also be given toward well-maintained second-hand machinery which can fit into the requirements of a CTF system, subject to scale and labour needs.

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. To increase capacity at sowing, consider whether speed can be increased without compromising establishment (e.g. using discs). Is the bin capacity sufficient, and can downtime be minimised with more efficient refilling and staff performance? This obviously needs to account for delays with breakdowns and rain that can occur.

Guidelines are available to help determine work rates and the areas covered using different equipment widths working at different speeds. Check out SPAA Factsheets or Precision Agriculture Apps and Podcasts for charts and calculators on machinery efficiency.

Table 2: Rules of thumb for machinery capital investment.

Machinery should be capable of sowing the crop in 21 sowing days
Machinery should be capable of harvesting the crop in 21 harvest days
Harvester capacity per annum 250 rotor hours
The seeding tractor should have six to eight horsepower per sowing tyne
Source: ORM Pty Ltd.

It can take anywhere from 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. If needed, obtain further assistance from an agricultural consultant with financial experience to provide a plan for machinery replacement schedules in the context of other business priorities.

It should be noted that modifying standard wheel spacings to suit a CTF system adds an extra cost. However, an increasing number of machinery manufacturers are now supplying three-metre axles as standard.

Table 3: Additional cost for three-metre axle width compared to a standard two-metre axle.

Machinery Added cost of 3m axle Comments
Boomspray, e.g. Goldacres 36m 6500L $529 - new
$1000 - retro fit		 Minimal cost difference between 2m standard and 3m axle with new machines.
FWA tractor, e.e. Case Magnum 250hp $3600 - spacers
$16,000- $20,000 - fixed axle		 Supplied by Boss Engineering, if buying a new Case tractor with front and rear duals, spacers come as standard.
Fixed front axle modification for tractors needing more strength for front weights or carrying implements.
Chaser bin, e.g. Finch 18t $2000 - retro fit New models come standard on 3m.
Airseeder cart - rear axle, e.g. Gason $3000 - retro fit Cost to retro fit can vary depending on machine. New models come standard on 3m, e.g. Simplicity quad cart or Horwood Bagshaw quad wheeled.
Belt-driven fertiliser spreader, e.g. Bredal K105 $3000 - new
$1200 - retro fit		 Minimal cost difference between 2m standard and 3m axle with new machines.

Practical options for growers

Once the decision has been made to convert to a CTF system there are a number of steps that should be planned and researched before investing in machinery or cutting up existing axles in the workshop. 

Ideally, speak with other growers or advisors who have already been through the process and learn from their experiences. Unfortunately, it’s not all beer and skittles when embarking on a CTF conversion, but persistence does pay.

Decide on the working width

Base the working width on the heaviest machine in the system, which is usually the header. It has the widest wheel base at three metres and is too costly or difficult to modify. Implement a machinery plan that incorporates current gear and scale with any future plans. There are numerous configurations from which to work from, but a 3:1 ratio is preferred due to its simplicity. Table 4 outlines the standard configurations for a 3:1 system:

Table 4: Standard CTF configuration for a 3:1 system.

Working width Header Airseeder bar Boomspray Spreader - urea Spreader - lime/gypsum Windrower
9.1m (30ft) 9m 9m 27m 27m 9m 9m
10.67m (35ft) 10.7m 10.7m 32m 32m 10.7m 10.7m
12.2m (40ft) 12m 12m 36m 36m 12m 12m
There are a number of alternative configurations (Table 5) that growers have adapted to suit their scale or existing machinery (e.g. 2:1 or 4:1), but still maintained the principle of staying on permanent tracks for all operations.

Table 5: Alternative configurations for CTF.

Working width Header Airseeder bar Boomspray Spreader - urea Spreader - lime/gypsum Windrower
9.1m (30ft)
(3:2:1)		 9m 18m 36m 36m 9m 9m
12.2m (40ft)
(3:2:1)		 12m 18m 36m 36m 12m 12m
13.7m (45ft)
(2:1 or 3:1)		 13.5m 13.5m 27 or 41m 27m 13.5m 13.5m
Measure your gear carefully, either in the workshop (seeder or header widths) or in the paddock (wheel track) to determine what you have already. In particular, determine the actual cutting width of the header or windrower and set the bar width to match to avoid leaving unharvested crop rows. It is better to measure twice and cut once.

Imperial or metric?

Decide if wanting to use metric or imperial. Unfortunately, 12m is not 40ft and accurate measurements need to be taken to ensure implements will match up. Growers in some areas, especially in Victoria and SA, have pursued imperial-based CTF systems using 120 inches rather than three metres as the base axle width (usually if using North American-made self-propelled boomsprays in their system). However, with most airseeder bars and boomsprays operating on metric (if Australian made), adding some overlap into the header front will ensure all crop gets collected. Ideally, for southern NSW use metric for measuring CTF systems (and stick with it!) to avoid any confusion or miscalculations.

Match additional operating widths

Complete the CTF system over time by matching additional machinery. For example, the air cart or chaser bin. Retro-fitting existing machinery is often done in farm workshops or by local engineering firms for minimal cost. Note that chaser bins can run on both tracks in a nine or 10.67m system with an auger extension on the header. However, in 12 or 13.5m systems the chaser bin generally needs to run off the tramlines on one track only. A side catcher attached to the edge of the chaser bin can alleviate this issue, or longer augers can now be purchased on newer model headers for additional cost.

Multi-purpose use of machinery is helping to reduce costs associated with CTF. For example, by using the sowing tractor for linkage spreading in winter and towing the chaser bin, or using the header front for both windrowing and harvest. The goal is less gear, but more hours, for each unit.

Modify load bearing axles

Convert machinery to suit permanent three metre wheel tracks by extending the axles of the tractor, spreader and boomspray. Cotton reels are commonly used for extending tractor axles to three metres and can be purchased through specialist engineering firms. Assess the suitability of converting your tractor prior to fitting an axle extension, because some smaller models or older machines are not suitable. Fixed axle conversions are also available for tractors with weaker front axle configurations or those doing load bearing work; they cost from $16,000 and are proven to last longer with better resale value.

Newer tractors and Australian-made airseeder bars or boomsprays now come with three-metre axles on warranty. North American machinery is not as simple and often requires modification which can range in cost from $2000-$15,000, depending on the skill of the operator and age of the machinery.

Field layout

Planning field layout (e.g. machinery runs) in the CTF system will improve operating efficiency and minimise runoff, erosion or waterlogging. Plan where chaser bins can turn around or where trucks can access during sowing or harvest. Compromises will exist, particularly in good seasons when extra grain means more unloading, but aim to stay true to the CTF system and utilise sacrifice areas such as old fence lines to help with long runs. In high rainfall areas, aim to drain wheel tracks toward grassed areas.

CTF can work in mixed farming systems in southern and central NSW, where the focus is on reducing compaction from heavy machinery, not from sheep. This is contrary to the ideals of other regions, but research data from Temora through FarmLink and CSIRO (Baxter article) found the impacts of compaction from sheep to be shallow and transient. Managing grazing to maintain a minimum of 70 per cent groundcover in summer and autumn was a greater priority to reduce wind or water erosion and increase infiltration from summer storm events. Removing stock from grazing crops when topsoil becomes waterlogged remains important.

Challenges and issues

As with any new concept there are numerous challenges that need to be tackled when moving into CTF. Many of the early CTF adopters have come up with solutions through their own innovations or by talking to a network of like-minded CTF enthusiasts. Some of the challenges faced in CTF and options for management include:

  • Deep and rough wheel ruts, especially in heavy clay soils. Constantly running machinery on the same wheel tracks is beneficial for creating a defined track, but deep rutting occurs during wet conditions and can cause water to pool. CTF farmers use a wheel track renovator with a toolbar on three metres which helps level and fill in rutted tracks.
  • Bare versus sown tracks. When starting out, CTF growers were initially keeping tracks bare to help define the area of compaction from the crop zone. With improved RTK reliability and grass weed issues on tracks, the majority of growers now sow tracks using a disc unit or shallow tyne to create competition.
  • Machinery fatigue with retro-fitted equipment. Cotton reels or front axle bearings have broken or worn over time and this is a significant risk for operators using farm machinery on highways travelling at speed. Ongoing maintenance checks are the only option and checking any retro-fitted axle extensions for cracks or fatigue, similar to any other machinery, is critical.
  • Large scale operations are difficult on CTF. Operations cropping 5000-6000ha have found it challenging for implementing a CTF program, usually owing to the large scale gear required to sow, spray and harvest. Compromises are available and configurations outlined in Table 5 are in use. This includes the 12m header/18m seeder/36m boomspray configuration with air cart and chaser bin capacity critical to making the system work.
  • Contractors not on CTF. For those growers who use contractors successfully in their business it can be challenging to implement a CTF system given the many different machinery configurations available. Work with your contractor over the long term so that they are aware of your plans for a CTF program and can potentially incorporate your plans into their machinery replacement schedule. The popularity of the 12m system works well with many contractors for sowing, spreading, spraying or harvest and many are now matched up for these systems.
  • Spreading lime or gypsum evenly on 12 or 13.5m widths can be difficult. There are a range of options available that can help spread ameliorants to widths greater than 10.67m. For example, using curtains or product that has been watered down.
  • Spreading chaff for systems wider than 10.67m can be difficult. Newer models of header now come with chaff spreaders that will throw beyond 10.67m in calm conditions, but older model headers will need to be retro-fitted with tools such as the Maximum Air Velocity (MAV) Redekop.
  • Chaser bin support for headers in high-yielding situations. Ideally, CTF systems work on one chaser bin per header in crops yielding above 2.5t/ha. In good seasons this is not practical and a second header is often brought in for one chaser bin. Aim to keep on tracks where possible and create sacrifice lanes across blocks where old fence lines existed, or utilise a mother bin to keep trucks away from the paddock.

The future for CTF

There are a number of developments that will further the cause of CTF and its benefits. Some of these are coming from grower innovation, but industry and machinery manufacturers are now realising the system benefits for their gear and market differentiation. Developments include:

  • Tracks replacing tyres to reduce the footprint in paddock, as well as minimise issues with tyre loading from heavier machinery. 
  • Harvest weed seed management is being enhanced in CTF systems with tools such as chaff lining and chaff decks. Weed seeds placed onto hostile traffic lanes are being left to rot or destroyed using LPG gas burners.
  • CTF has an ideal fit for the shift to smaller autonomous machinery. Trials have already proven successful using camera sprays on small units applying low volumes of herbicide.
  • CTF allows for the establishment of farm-scale trials that can be both replicated and randomised, with all plots of equal size providing a useful source of large-scale trial data that can be linked into precision agriculture platforms.

Conclusion

CTF is slowly gaining a mainstream presence. Although adoption remains relatively low in southern NSW, it has been taken up by many leading growers, with others looking over the fence. The lack of on-farm CTF research in this region is holding back many advisers from including it in their programs, despite positive evidence from other areas. 

CTF is a complementary practice to no-till systems, and along with summer fallow management and early sowing, helps buffer the extremes of climate to provide greater yield stability.

Increased machinery weights and tighter operating windows mean many growers are now in the paddock spraying, spreading or harvesting regardless of soil condition. This is leading to soil compaction which is costly and difficult to remove with deep tillage.

The increasing reliance on retained subsoil moisture for late season grain fill has made the industry focus on any subsoil constraints that could be limiting rooting depth. Managing constraints such as compaction, acidity or sodicity is critical to improve the availability of soil water for crops.

Managing the machinery changeover for the move into CTF is challenging and balancing the need to modify or buy new gear requires careful financial analysis. It will take time to reach the objective of having all machinery matched, but often growers need to compromise in the short term knowing that a profitable CTF system can be achieved in the longer term.

Useful resources

Acknowledgements

Bindi Isbister, Department of Agriculture and Food Western Australia
James Hagan, DAFWA
Tim Chamen, CTF Europe

References

Kingwell, R, & Fuchsbichler, A (2011) The whole-farm benefits of controlled traffic farming: an Australian appraisal. Agricultural Systems, Vol. 104, issue 7, pp 513-521.
Bowman, K (2008) Economic and environmental analysis of converting to controlled traffic farming. 6th Australian Controlled Traffic Farming Conference, 2008
Chan, K et al (2006) Agronomic consequences of tractor wheel compaction on a clay soil. Soil Tillage and Research. Vo. 89, Issue 1, 13-21
Ellis, T et al. (2011) Soil and yield improvements from controlled traffic farming on a red chromosol were similar to CTF on a swelling black vertosol. 5th World Congress of Conservation Agriculture, Brisbane, 2011.

Tullberg, J et al (2007) Controlled traffic farming – from research to adoption in Australia. Soil and Tillage Research. Vo. 97, Issue 2, 272-281.

Contact details

Greg and Kirrily Condon
PO Box 73 Junee, NSW 2663
0428 477 348 (Greg)