Soil loses out from wheelings and tramlines
Compaction from wheelings and tramlines can impact on crop yields, warns senior ADAS soil scientist Dr Martyn Silgram who has been undertaking in-depth studies in this area over the past ten years.
Growers need practical, cost-effective measures to limit these losses and help them achieve yield targets.
Martyn says: “Tramlines are, of course, an important management tool to support crop management practices in cereal crops.
“However there are times, such as in the autumn when soil is relatively bare and moist, when management practices needed for agronomic reasons, such as crop spraying, may also inadvertently also increase the risk of a number of problems.
“These include soil compaction, surface runoff, erosion, and nutrient loss.”
Land particularly at risk includes fields with moderate slopes, on longer slope lengths (50m or more), and in areas with moderate or high rainfall or with vulnerable erodible soil types.
Martyn’s studies in cereals have assessed four alternative tramline management methods in replicated hillslope-scale trials against an unmanaged control across four sites and four seasons. He has conducted similar trials on row crops including potatoes.
“For winter cereals, we have found that using novel equipment as part of autumn field management operations, including Michelin’s Very Flexible (VF) low ground pressure tyres or a novel self-propelled rotary harrow unit developed by Great Plains and Househam sprayers can significantly reduce soil compaction, runoff, and erosion- by 50 per cent or more.”
Results indicate that practical management options to minimise risks include:
- Increasing tramline spacing
- Minimising compacted wheel marks using low ground pressure or specialist VF tyres
- Avoiding channelling water down wheel-marks (careful timing of field operation)
- Using the correct tyre inflation pressure for the tyre, field operation and axle load
- Use of correctly inflated Very Flexible (VF) tyres (which typically operate at half the pressure of conventional tyres, and which operate at this same pressure on both field and road)
- Use of a novel small ground-driven rotary harrow unit attached to the rear of a crop sprayer and hydraulically linked to the tractor cab using a simple toolbar frame. This has low draft requirement, does not affect fuel use, and punctures the soil in several places across a wheeling, increasing infiltration without affecting vehicle traction. It is only required when soils are moist such as when crop spraying in autumn.
- Use of a novel surface profiler/roller unit attached to a toolbar. This creates a convex profile across the wheeling which sheds water back into the crop area, and avoids it channelling down the wheeling
Martyn explains that his work found that VF tyres were effective at reducing compaction, runoff, and erosion risk on a wide range of soil types (light, medium and heavy mineral soils).
Tramline management using the rotary harrow or surface profiler/roller units was highly effective on light (e.g. loamy sand, sandy loam) and medium (e.g. silty clay loam) soils.
Results from heavy clay soils also showed benefits of these techniques.
“Heavy soils are generally structurally stronger and more able to withstand axle loads when they are dry, and therefore are less prone to compaction problems in dry autumns.
“However, they quickly smear and rut when wet, so I would suggest that, where possible, traffic is avoided under these conditions.
“This highlights the importance of careful timing of field operations on heavier soils. Both rotary harrow unit and surface profiler/roller unit have also been evaluated on row crops such as potatoes in the spring and they are also highly effective in reducing compaction and erosion in those situations and times.”
Martyn also notes that the alternative of not using tramline at all, but drilling the whole field area including the part intended for using for field operation traffic later (using GPS devices in tractor cabs) does not solve the problem.
His monitoring programme has shown that compaction, runoff and erosion still occur under these circumstances. “These results reveal that it is the farm traffic operations (such as crop spraying), and not the bare soil and lack of vegetation cover, which is likely to be the primary cause of the increased risk in UK conditions.”
Tyres play a major role in avoiding compaction.
“Very Flexible tyres such as the Michelin Xeobib are claimed to have a lifetime of around 9,000 hours compared with 6,000 hours for conventional tyres, although they do cost more to purchase.
“Moreover, manufacturers have reported overall fuel savings of around 15 per compared with conventional tyres. Sub-soiling costs are likely to be significantly reduced. The key advantage of investing in such tyres is that you get the benefit of using them across the entire farm, not just to help reduce compaction in winter cereals, and our independent assessment has concluded that there is a modest overall net cost benefit of their use at whole-farm scale, notes Martyn.
Note: This study has been led by ADAS UK Ltd. supported by Defra, AHDB (HGCA) and the Sustainable Arable LINK programme with major industrial partners including Simba (now Great Plains), Michelin, Chafer, Househam and AgCo.