Taking Soil Compaction Out of the Equation

Those of use who didn’t grow up in agricultural families may be unaware of just how important soil quality is to arable farming. And as the size of farms grows and the agricultural industry becomes an increasingly professional business, so the use of modern machinery is also increasing. That’s why Michelin invited journalists to a farm in Leicestershire to learn about how products like its Axiobib tractor tyre prevent the problems that are associated with soil compaction.

We’ve all driven past fields with water-logged tyre tracks running across them. But did you know this can be a sign that poor tyre choice has led to lower levels of soil being compacted, which in turn hinders drainage and reduces crop yield? Neither did we, so it was a good job Michelin had invited the Soil Management Initiative’s (SMI) resident soil expert, Dr Alistair Leake, along to explain the science behind the theory. (The SMI is a non-profit making, independent organisation dedicated to promoting the adoption of systems designed to protect and enhance soil quality, resulting in agronomic and economic benefits for farmers. The Environment Agency, John Deere and Michelin are just three of the 22 SMI members.)

Dr Leake’s philosophy is that successful arable farming is all about working the top few inches of soil with skill rather than churning up and compacting the whole profile with the brute strength of horsepower alone. As you can imagine tyres are vital to correctly striking this balance.
According to Dr Leake, it is becoming increasingly important that farmers do successfully strike this balance as rainfall patterns have changed significantly in recent years. While he refused to comment on his opinion as to whether or not this was down to man-made global warming, Dr Leake was clear that the evidence shows that British rain is less evenly distributed than it used to be. Total annual rainfall is said to be the same, but now when it rains, it really does pour – causing drainage and leeching problems. The point is: using badly chosen or over-inflated agricultural tyres reduces any product’s floatation characteristics and therefore increases soil compaction. And soil compaction is bad because it costs farmers money in terms of reduced yield; it costs to repair and correct; and overusing horsepower uses more fuel, again costing farmers money.

Here’s where good floatation tyres come in. Selecting the right products and pressures for agricultural use is not as simple as just getting the right tyre size. Michelin’s advice is: “For best results consider the operational needs.” This means: Soil condition, ground pressure and wheel load; field power (torque) needed at the wheels; and road use and speed must all be considered.

Michelin offers a comprehensive range of floatation enabled products to cater to the various needs of farmers and agricultural contractors – the AgriBib, MachXBib, MegaXBib, CargoXBib, XMCL, XeoBib and AxioBib. The latter two are so unique in their floatation properties (their ability to run at just 1-bar, for example) that the ETRTO developed the VF (very flexible) and IF (improved flexibility) sidewall markings in order to adequately describe them. Michelin demonstrated the tyres’ particular aptitude in relation to soil compaction by driving various configurations of machinery across a fresh field and measuring the depth of tracks left by the tyres.
For the purposes of the demonstration Michelin hooked up a Xeobib-equipped tractor to a fully laden trailer before driving across the aforementioned field. On this occasion the results were particularly impressive because the previous evening’s rain appeared to have done its level best to make the soil sticky in time for demonstration day. Despite this, the rear axle 650/65 R42 (21 psi) AxioBib tyres, carrying 4200 kilos each side made impressions just 7cm deep. On the trailer, the CargoXBib 560/65 R22.5 (30 psi) tyres – set up for 50 km/h transport – and carrying approximately 4 tonnes a tyre made tracks of between 9.5 and 10 cm. However, according to Michelin UK’s agricultural technical manager, Peter Debenham, these depths could have been three-times as much with supersingles.