Case Study 3

Farm Details

360 ha on silty loam and limestone brash soils with crops grown principally for seed. These include:

  • Sugar beet (grown on the lighter soils)
  • Winter wheat
  • Peas (grown for vining seed)
  • Spring beans
  • Spring and winter oilseed rape
  • Oats
  • Linseed
  • Herbage (likely that this will be replaced by grass margins if 5 m headlands are allowed under the new E.U. set-aside scheme)

Rotation and Crop Establishment

There is no fixed rotation. Challenges and opportunities are managed on a daily basis. Spring crops are used to improve weed control, but with direct drilling, the system is often fragile if spring conditions are cold and wet. Third wheats are avoided if possible and set-aside includes both rotational and permanent. Sugar beet occupies about 10% of the cropped area.

Other than sugar beet, crops are usually direct drilled. Prior to sugar beet, the land is ploughed and cultivated with two passes of a Dutch harrow and crumbler roller combination. After sugar beet, severely compacted areas are deep loosened and the whole area then cultivated with two passes of the Dutch harrow combination. For other crops, direct drilling is adopted providing any weed problems are under control.

Equipment

Spray and fertilizer are applied on a 12.5 m tramline. This is matched with 4.13 m Accord and John Dale drills. The latter has two tine openers slightly offset from each other to provide a narrow band of seed. Row spacing is 245 mm.

Stale seedbed tillage is provided by a Phoenix soil driven harrow which can be adjusted to cover 12.5 m. This is pulled by a New Holland 7635 tractor.

Cereals harvester is a Claas Maxi Dominator 108SL with a 5.17 m cutterbar. Two trailers are used to haul the crop.

Sugar beet is grown on 20” (0.51 m) centres and is harvested by a contractor presently using a Vervaet "Beet Eater" 9 row harvester. This has three axles with wheels set to match across the width of the machine edge to edge. The beet haulage trailers have three axles all equipped with 650/55-26.5 flotation tyres.

More specific details are given in the table below.

Equipment dimensions

Description Working width, mm Axle gauge, m Tyres
Front Mid Rear Front Mid Rear
Claas Dominator harvester 5.171 2.91   2.65 30.5R32   500/650-26.5
Phoenix cultivator up to 12.5 0.55     11L-5F1    
Dale drill (4 wheels about C/L) 4.13 0.74     10/75-15.3    
New Holland 7635 tractor   1.52   1.56 11.2R28   13.6R38
John Deere 3350 (drill tractor)   1.62   1.8 13.6R28   18.4R38
Ford 7610 tractor (spray/fert)   1.56   1.65 8.25R16   18.4/15-30
Trailer 1   1.85     18-19.5    
Trailer 2   1.89     18R19.5    
Vervaet 9 row "Beet Eater" sugar beet harvester 4.57 3.7     800/70R38    
    2.9     800/70R38  
      2.1     800/65R38

1 Unloading auger reaches approximately 7 m laterally from the harvester centre line

The figure below shows these data in graphical form.

Graphical presentation of the wheel track and tyre data for the existing farm equipment.

Click the image to view a larger and clearer diagram.

Possible courses of action to achieve a high element of CTF

Least Cost

The course of action suggested here is based on the assumption that Trailers 1 & 2 cannot easily be modified in terms of their track width. The tractors, which are assumed to have a reasonable range of wheel track adjustment, are therefore modified to fit in with the overall track width of the trailers. It is recognised however that wheel track settings will have to be changed for drilling the sugar beet crop and in this least cost scenario, sugar beet will lie outside the CT system, both through this fundamental requirement (row spacing of 20") and the fact that the wheels of the harvester span the complete machine (see Table above).

Tractor Modifications

Increase JD rear wheel track to 1.87 m and front to 1.77 m.

Increase Ford 7610 rear track to 1.88 m and front to 1.61 m. Replace rear 18.4/15-30 tyres with 16.9R34 radials (430 mm width and approx. 25 mm greater diameter).

Increase New Holland 7635 rear track to 1.70 m and front to 1.72 m.

Tramline track width is now 1.86 m and wheeled width per track is approximately 430 mm (assuming new tyres fitted).

Implement Modifications

Increase drill width to 5.0 m by adding four coulters (metering outlets and space are available to do this). Although this will not match the cutterbar of the harvester exactly (5.17 m), it will allow a margin for error. It may also be advisable to make minor adjustments to the drill coulter spacing around the wheel tracks so that a single drill row is blocked off, either on every pass if all wheetracks are to remain with a marker line, or on every third pass to provide a mark for the sprayer and fertilizer spreader whose width will need to be increased to 15 m. Moving the implement wheels to match the primary track gauge (1.86 m) will be a significant benefit if this is feasible.

Equipment layout following the least cost option - trailers as found but tractor wheel track settings and some tyres changed

Click the image to view a larger and clearer diagram.

Field Operations

As a result of the tractor and equipment modifications, permanent tramlines at 5.0 m spacing will be set up (see figure above). These represent a 17.2% loss in cropped area compared with an existing 8.2% loss, both figures based on the actual width of tyres used (430x2x100/5000 & 516x2x100/12500). Depending on whether some of the wheel tracks are sown or not, this additional 8% loss represents a worst case scenario, which according to yield data, will be compensated by an increase in yield per se, and be augmented by additional gains from timeliness due to lower draught and faster operations. On some occasions wheel track sowings may have a slightly retarded growth, but this has never been found to be a major problem at harvest.

If soil moisture at harvest is high (around the plastic limit) and the wheel tracks of the harvester outwith the main tramline are creating ruts, it may be necessary to carry out some repair specifically in this area. Fracturing the soil to around 300 mm depth may often be sufficient, with care being taken not to disrupt the permanent tramlines. Pulling soil into the tramlines during this operation could be beneficial to make up for sinkage due to consolidation.

Intermediate Cost

This approach looks at changing the farm-based trailers within the system and again matching the tractor track widths to the trailers. In an attempt to bring the establishment of sugar beet into the CTF system and the possibility of direct drilling this crop, trailers on a track width of 2 m are suggested, and these are widely available commercially.

Tractor Modifications

Increase JD rear track width to 2.03 m and front track to 1.91 m. Consider replacing 18.4/R38 tyres with 16.9/R34s.

Increase Ford 7610 rear track to 2.00 m and front to 1.80 m. Replace rear 18.4/15-30 tyres with 16.9R34 radials (430 mm width and approx. 25 mm greater diameter).

Increase New Holland rear track to 1.95 m and front track to 1.90 m.

Tramline track gauge is now 2.00 m and the wheeled width per track will be 430 mm (assuming the JD tyres have been replaced, which in this case is more beneficial because the trailer wheels are now matched and will not come outside the main tramline).

Implement Modifications

As in the least cost option, the drill width is increased to 5.0 m to approximate to the cutting width of the cereals harvester, and the spray and fertilizer application equipment are increased to 15 m. Moving the implement wheels will again be beneficial if this can be achieved without major cost.

Equipment layout following the intermediate cost option - new trailers with a 2 m track width and tractor wheel track settings and some tyres changed

Click the image to view a larger and clearer diagram.

Field Operations

As in the least cost option, tramlines at 5.00 m spacing will be set up with the attendant and identical proportion of wheel tracks. The area outside the main wheel tracks which is wheeled by the harvester will however be slightly less than in the previous option.

Benefits

For those areas that receive no traffic at any time, there are likely to be crop yield increases in the order of 10% compared with conventional practice. This figure is very much an average because the loss of yield due to a random traffic system depends on the long term history of soil damage (axle loads and ground pressures) and how much soil damage was caused last season, the latter being governed to a large extent by how moist the soil was when operations were carried out. In the case of direct drilling, yield increases in the first few years may be more modest because soil remediation will rely on natural processes.

Direct sowing of crops in the spring will be more reliable within a CTF regime. Experience on clays suggests that this operation is particularly risky in the presence of traffic when soils are slow to drain and to warm up in the spring. Field trials with CTF have shown that as a result of improved soil structure, drainage is improved and crop growth in the spring is earlier and more rapid.

Cultivator and drill draught requirements will be reduced substantially on the non-trafficked areas. Not only will this allow a wider drill to be pulled with perhaps little additional power, but there are also likely to be benefits in terms of reduced tine and coulter wear and easier penetration in dry conditions.

Friable and usually moist seedbeds should always be available on the non-trafficked soil. Not only will these provide more rapid germination and growth of the crop, they may also deter or negate the damaging effects of seed predators such as slugs. These are often able to follow the smeared slot created by drills in compacted topsoils and these will be absent in the new conditions. "Stale" seedbeds (to promote germination of weeds) will also be easier to create and less likely to be dependent upon weather. Similarly, crop seed rates can be lowered in response to better quality seedbeds.

Where operations are carried out without markers, and particularly those using wide equipment, adhering to controlled traffic wheelways will avoid inefficient under- or over-lap.

Drawbacks

If none of the permanent wheelways are sown, there may seem to be a large proportion of the field without crop. As has been stated however, there is more likely to be an increase in overall yield than a depression.

There is limited experience of permanent wheelways in moist temperate climates, but we do know that they are significantly different from annual tramlines because with an element of repair, they improve with time. Important to their early success however is not to introduce them on newly loosened soil.

Controlled Traffic Farming requires additional discipline compared with random wheeling. It also means that all operations are carried out parallel to the tramlines. Although this is unlikely to be of any significance as far as the limited amount of cultivation required in a CTF system, it may cause problems with the harvest of the peas for example. In some instances these need to be gathered against their direction of lie. Only experience will reveal the extent of this potential problem.

Outcome

The grower has considered the options and will work towards the introduction of the 5 m system. The trailers however will be set to a track width of 1.75 m, which is achievable without a great deal of modification, and fits better with with a drill row spacing of 250 mm.