MONITORING and adjusting farm machinery tyre pressures regularly to suit each application has potential to reduce soil compaction, wheel track rutting, fuel consumption and abnormal tyre wear.
That was the message to farmers, attending the recent National Soil Amelioration/Controlled Traffic Farming Conference in Perth, from agricultural tyre expert Kieran Grey.
Mr Grey is founder of Evolution Agri Services, Australia's only dedicated agricultural tyre inflation company which supplies Germany-sourced PTG inflation systems.
Working soft ground with tractor and implement tyre pressures still set at road pressures was like "driving up hill all day", Mr Grey explained to farmers at the conference.
Monitoring tyre pressures at least daily was particularly important on equipment normally operating on low pressures in paddocks with a varying load - such as self-propelled or tow-behind sprayer units or spreaders - where the reducing load can help disguise a tyre losing pressure.
"If you are are running 10psi (pounds per square inch air pressure) in the paddock and the pressure drops to 8psi, that will make a massive difference to how the tyre performs under load, compared to losing 2psi in a tyre running 26psi road pressure," Mr Grey said.
Taking time to reduce tyre pressures to the tyre manufacturer's recommendation for soft ground before starting work in a paddock helped reduce a "bulldozing effect", where tyres at higher pressure built up a mound of soil or sand in front of them in soft going and pushed that along as they rotated, he explained.
Although seemingly counter-intuitive, reducing tyre pressures to about 50 per cent of road pressures in soft going reduced rolling resistance by limiting that build up in front of the tyres.
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Lower pressures lengthened each tyre's footprint - by up to 34pc with a 50pc pressure reduction - rather than widened it, Mr Grey explained.
Increasing the tyre's contact area with the ground helped improve traction under load and limited wheel slip, but importantly, helped better distribute axle loadings over a bigger area, he said.
With heavy equipment, the longer footprint helped maximise tyre "flotation".
This encouraged the tyre to roll over the surface rather than sink in and cause rutting, Mr Grey said.
"Every five centimetres of rutting depth is the equivalent (in terms of fuel usage) of a 5pc uphill gradient," he said.
Critically, by increasing flotation, "optimised" lower tyre pressures also helped limit the depth of soil compaction, particularly on controlled traffic paddock tramlines and in high traffic areas, reducing need for and expense of periodic tramline renovation, Mr Grey pointed out.
"With tyre pressures optimised for the job being done, you can look at a reduction of up to 20pc in tyre wear and up to 15pc in fuel usage with, in a controlled traffic farming operation, a debatable 25-30pc yield improvement attributed to non-compaction and greater moisture penetration," he said.
Optimised paddock tyre pressures were a balance between traction on drive axles and flotation, he said.
"Normally traction and flotation contradict each other, but it is possible to have both working for you with weight when you are on soft ground in the paddock," he said.
"It's a balance, if you get pressures right for traction then you increase your speed and get more work done for the amount of fuel you use.
"If you get them right for maximum flotation you limit the depth of soil compaction and increase yield."
There were many variables in tyre pressure optimisation which farmers need to consider, including tyre size and sidewall specification, ground speed, axle loadings and weight distribution, Mr Grey said.
If farmers felt there was insufficient information on the tyre sidewall or on the tyre placard to make decisions on optimising pressures, they should consult an agricultural tyre expert, he advised.
Modern agricultural tyre design also helped balance load carrying capacity and soil compaction reduction by having controlled sidewall flex characteristics which enabled lower pressures to be used, he explained.
IF and VF references in agricultural tyre specification stood for increased flexion and very high flexion.
An IF tyre was capable of carrying the same weight as a standard tyre, but at 20pc less pressure, or alternatively Mr Grey explained, could carry 20pc more weight at the same pressure.
With a VF tyre, the difference in operating pressure or carrying capacity at the same pressure was 40pc, he said.
Setting agricultural implements up with the correct tyre pressures could also maximise their performance in terms of accuracy - from sowing depth to harvest height.
"We have all been guilty of overlooking the effects of tyre pressures and it usually takes a few questions to link the machinery, tyre and application together," Mr Grey said.
"I have been involved in farm machinery my whole life and it was a really big light bulb moment when I looked at what I could have improved over the years through adjusting tyre pressures."
While tyre pressures needed to be monitored and adjusted for paddock work, it was just as important to pump them back up for driving on roads during transport between paddocks and farms, Mr Grey reminded farmers.
Correct road pressures were essential for safe road operation because they affected vehicle stability, he pointed out.
They also helped reduce heat build up and tyre wear while reducing fuel usage, he said.
