Effect of four alternative front tyres on seedbed compaction by a tractor fitted with a rear wheel designed to minimize compaction☆

The increase in soil bulk density and cone resistance and the rut geometries produced by a tractor fitted with a “Yieldwheel” on the rear, and each of four alternative front tyres, were measured in a simulated seedbed in an indoor soil tank. The four tyres were a conventional cross-ply, a wide section cross-ply, a wide section radial and a very wide section low pressure tyre. With front-end weights fitted to the tractor and at low draught force, both the radial and low pressure tyres compacted the soil significantly less than did either of the two other tyres. Without front-end weights, there was little difference in seedbed compaction caused by the four tyres. Reduction of the tyre pressures to half their minimum recommended values had no significant effect on either the magnitude or rank order of the soil compaction effects. Rut geometries were always similar for all four wheels because of the overriding effect of the rear wheel.