THE merits of 4WD tractors fitted with tyres compared with those with single tracks in terms of soil compaction continues to be debated worldwide.
Soil compaction has been shown in recent years as having serious effects on crop yields.
While compaction can be useful to ensure good soil-to-seed contact to ensure consistent germination, problems arise when wheel traffic from tractors and equipment firms soils beyond what is considered the best conditions for germination and root development.
According to New Holland technicians, it has long been recognised that overly compacted soil restricts root growth and causes poor root zone aeration and poor drainage.
While some soil compaction is inevitable, new studies have found that croppers can minimise the damage by using proper tyres and sound soil management practices.
Agricultural researchers at the Ohio State University and the North Dakota State University in the US have performed similar studies over the past decade to assess the impact on soil compaction from dual radial tyres and rubber tracks.
The basis of the tests was a comparison between two 4WD tractors, one fitted with dual radial tyres that were properly inflated and the other with over-inflated tyres, and two Cat Challenger tractors with rubber tracks.
The researchers found the tractor with properly inflated dual radial tyres ranked best, the tractor with over-inflated dual radial tyres ranked worst, and the performance of the rubber tracked tractors fell in between.
And here's why: When an implement is being pulled, the weight transfers from the front axle to the rear axle.
On a tractor with tyres, this reduces the load on the front tyres and only slightly increases the pressure under the rear tyres because the tyres spread out to distribute the additional weight.
Radial tyres increase the footprint within increased loads and have the ability to maintain virtually the same ground pressure with different loads.
Ground contact pressure is directly related to tyre pressure.
An over-inflated tyre has a smaller footprint, greater contact pressure and so greater soil compaction results.
On a tracked tractor, weight transfers in the same way, except the track does not have the ability to spread out to distribute the additional weight.
The result is a marked increase in ground pressure under the rear wheel.
According to New Holland, ways to overcome this problem include reducing inflation pressures of tractor tyres to the manufacturer's minimum suggested levels for the load.
Consider the weight of the load.
Mechanical front wheel drive tractors and 4WD tractors can pull heavier loads at lower levels of wheel slippage than two-wheel drive tractors.
This lessening of slippage will help reduce compaction.
Ballast the tractor properly and remove any unnecessary weight.
Always ballast with iron, as a tyre filled with liquid cannot flex and will cause more compaction.
For the sake of the soil, work in the driest paddocks first and stay off areas that are too wet.
Heavy axle loads, such as grain carts and combines, can cause deep soil compaction, so keep traffic to specific areas and stay in these as much as possible to minimise damage.
When possible incorporate no-till or minimum till practices.
Finally, be aware it may take soil many years to recover from compaction.