In the first part of our blog series, we described the starting situation and the problem of soil compaction, and touched on possible starting points for solving it. In this second part, we look at these points in more detail — with figures and examples.
Comparing tyres of different profile and diameter
Large-diameter, high-profile tyres have an advantage over wide-profile tyres when it comes to load capacity and contact area. Why is that?
To illustrate this, let’s look at a worked example.
Take, for instance, a 650/75 R38 tyre compared with a 650/65 R tyre of the same diameter and width
If the tyre profile were taller – as with a 650/85 R38 tyre, for example – the load limit could be increased by 1155 kg, given a larger outer wheel diameter. Correspondingly, the increase in air volume has a positive effect in reducing pressure on the soil.
If we compare these tyres (650/85 R38) with wide-profile tyres (900/60 R38), it becomes clear that the load limit, despite an identical outer diameter and rim diameter, is only somewhat higher – by 700 kg. That’s disproportionate to the higher tyre cost and wear costs (DLG Merkblatt 356, p.13).
Large-diameter wheels compact the soil less than wheels with wide-profile tyres.
“Changing” the tyre profile
Large-diameter, high-profile tyres have the advantage that, at low air pressure, they can “flex out,” meaning they increase their contact area. Thanks to this, a vehicle travelling on roads with high air pressure and a small contact area needs less fuel.
A good example is a combine harvester, which cannot use wide-profile tyres (say, 800-900 mm) because of the header width, which keeps growing wider, but which does have room for large-diameter wheels. In addition, to protect the soil, preference should be given to trailed implements – sprayers or precision seeders.
What else is worth knowing?
Summing up both blog posts, the key points for modern agricultural machinery that helps conserve soil are:
- A greater air volume helps increase the wheel load limit. At the same time, low tyre pressure while working in the field reduces soil compaction (an automatic tyre-pressure control system).
- Using large-diameter, high-profile tyres offers better advantages than wide-profile tyres.
What’s next?
In the next part of the blog, we’ll cover practical solutions for minimizing soil pressure. How can you cut costs and boost productivity? Why are wheel tracks so damaging to a field? We’ll answer these and other questions in the next blog post. Stay tuned…
