Research and experience has shown that by fitting rubber track systems to heavy machinery such as tractors, combines, beet and potato harvesters, farmers can alleviate damaging soil compaction.
Soil compaction continues to be a serious problem on many UK farms. It has been proven to reduce crop yields, increase tillage-related energy, time and costs, diminish – if not totally negate – soil water infiltration, and amplify the problems associated with run-off and flooding. The true cost of soil compaction to UK agriculture every year is estimated to be an eye-popping £350 to £500 million!
It occurs when the ground pressure on the soil exceeds its ability to resist and it can affect both the upper layer of soil (the topsoil) and soil to depth (subsoil). When soil particles are compressed together too tightly, they form a solid, impermeable layer. This restricts the movement of water and essential nutrients down through the soil profile. It also impedes root development, inhibits earthworm activity and excludes the air vital for an environment rich in beneficial micro-organisms.
The images above show deep cultivation pans that have formed a permanent barrier to roots limiting the effective soil depth in the field. The profiles have clearly broken away at the top of the compacted layer. Root growth below and through the layer is minimal. The structure is dense and blocky. Cracks in the soil can be horizontal, rather than vertical.
Restricted root development inevitably impacts on plant health and yield as well as reducing drought resilience and nutrient uptake. Compacted soil is at greater risk of erosion as it is less porous, which means it is less able to absorb water and resist surface run-off. Erosion removes soil, nutrients and pesticides from the field and potentially into rivers. Wheel imprints in tramlines on sloping arable land are a particular problem. They basically create channels for rainwater run-off. Research has shown that 80% of run-off in arable fields on sloping land comes from these compacted tramlines.
Traffic from heavy farm machinery is the main cause of compaction, although excessive livestock trampling can also be a factor. There are a number of ways to minimise machinery-induced soil compaction. Controlled Traffic Farming (CTF), for example, utilises permanent traffic lanes, which are designed to be the only parts of the field that are exposed to machinery tyres. Although highly effective for reducing the effects of compaction in the majority of the field, the CTF system can be complicated to plan and set up, often requiring the use of precision navigation tools and auto steering technology.
Where possible and if the farming system allows, reducing the number of passes can also significantly reduce compaction rates.
For many farmers, however, adapting their machinery to mitigate ground compression is an easier and more viable solution.
Tracks can make the difference
One of the most effective machinery modification strategies is to replace wheels with a rubber track system. Wheeled vehicles generally disturb soil and create deeper ruts than tracked vehicles due to their lower contact area. Tracks however, spread the machine load over a greater area of soil surface, potentially reducing rut depth by up to 40% compared to extra wide or soft tyre options. This is in spite of increasing the mass of the vehicle or trailer by as much as 12%. Research carried out in The Netherlands shows that, even when compared with modern, extra flexible, UltraFlex tyres, tracks exert significantly less pressure on the soil.
A three-year UK trial, conducted some years ago but still relevant today, recorded an average 4.2% annual wheat yield benefit from using tracks compared with equivalent weight wheeled and tracked tractors. While tracks had only a marginal effect on soil density down to 50cm over the three years, the use of conventional wheels produced a pan at 25-30 cm. Studies have also shown a 63% reduction in the draught force required for sub-soiling following trafficking by tracked rather than wheeled combines due to a smaller increase in soil strength at depth.
Track systems may not be cheap, but they do represent an excellent investment when viewed against the potential costs of reduced yields and the increased operating costs associated with working compacted soils.
Top 10 Tips for Reducing Compaction
