20 March 1998

Reduced pressure savings

FAILURE to adjust tyre pressures when wider tyres have been fitted to enable heavier axle loads to be carried can cause irreparable soil damage.

Thats the message from a recent Institute of Agricultural Engineers conference which revealed use of over inflated, oversize tyres has led to exaggerated soil stress at ever increasing depths.

"Compaction problems used to be confined to the top-soil but recent tests have shown the problem is going deeper as a result of operators not adjusting tyre pressures to suit the task being done," explains Tim Chamen of 4Ceasons Consultancy.

Axle loads

"The problem stems from increased axle loads these wider tyres now allow, and failure to reduce the inflation pressures to the lowest recommended setting for the load being carried," he says.

Mr Chamen points out farmers must seek professional advice from their tyre suppliers or manufacturers to determine which inflation pressures best suit a given task.

"If yields are to be maximised, then the topsoil and subsoil need to be looked after. It is often the case that compaction of this type goes unnoticed."

"The needs of tractor and plant are very different," he explains. "Tyres like a firm surface on which to get good traction, while plants prefer a loose soil structure to promote good growth. And to get the best results, a compromise has to take place."

Damage repair

According to Mr Chamen, the level of sub-soil damage taking place will require a greater management demand to repair and he fears prolonged operation of tractors with overinflated tyres will eventually damage the soil structure beyond the point of recovery.

"Larger tyres and increased loads are all very well, but unless inflation pressures are correctly adjusted to manufacturer recommendations – for specific tasks – soil compaction will only become worse, not better," he warns. &#42

Tyre makers recommended inflation pressures should be followed to avoid irreparable top-soil and sub-soil damage, warns Tim Chamen.