Much of Queensland’s cropping and grazing lands are affected by, or susceptible to, subsurface compaction. Subsurface compaction generally occurs between 10 and 40 cm depth, and is caused by the compression of the soil by agricultural machinery or stock traffic. A compacted soil lacks the interconnected air spaces that are essential to the movement of water, gases and plant roots. This can limit plant yield and increase the energy required for cultivation. (See Subsurface Compaction—Queensland factsheet).
There are limited options for ameliorating subsurface compaction. However, management practices can be implemented to reduce or avoid subsurface compaction.
When a paddock is trafficked in the traditional manner by a variety of tractors, harvesters, implements and trucks, all with different wheel spacing, a considerable amount of soil compaction and inefficiency occurs. Reducing this trafficking will reduce soil compaction.
Controlled traffic farming is a system where all field traffic, including the harvester, is restricted to permanent wheel tracks referred to as traffic lanes or tramlines (figures 1 & 2). The wheel tracks enable equipment with compatible wheel spacing to travel across a paddock using the same path for each operation. Global Positioning Systems (GPS) are often used to steer the machinery and keep it on the precise track.
Figure 1: A crop being harvested with the chaser bin driving on permanent wheel tracks. (Photo by Paul Blackwell, DAFWA).
Figure 2: A crop being harvested with the chaser bin driving on permanent wheel tracks. (Photo by Paul Blackwell, DAFWA).
When combined with zero tillage, the advantages of CTF include:
In certain circumstances, there may be some disadvantages associated with CTF systems, including:
New approaches to avoiding the risks of soil loss from heavy rainfall for downhill controlled traffic systems are being evaluated. Widespread use of techniques such as tramline farming, controlled traffic and auto-steer means that working on the contour is often not practical. Queensland research has shown that controlled traffic systems working downhill on slopes up to 2 % can reduce the incidence of gully erosion from intense storms compared to contour planting, provided there is good ground cover and water infiltration.
Where the soil is compacted or groundcover levels are low (especially after grazing), runoff from downhill systems can be larger than when working across the slope. This indicates a need for appropriate earthworks to control the rate of overland water flow and minimise the risk of soil erosion from intense rainfall events.
Technical difficulties of grass weed control and rutting in permanent tramlines still persist, but chaffy (furry) tramlines, zero tramline disturbance and better tyre choice may offer improvements, as well as improved management of water flow.
Department of Environment and Resource Management (2011) Controlled traffic farming—soil conservation considerations for extensive cropping, Land Series Sheet L146, Queensland Government, Brisbane.
The Controlled Traffic Farming website.
The National Soil Quality Monitoring Program is being funded by the Grains Research and Development Corporation, as part of the second Soil Biology Initiative.
The participating organisations accept no liability whatsoever by reason of negligence or otherwise arising from the use or release of this information or any part of it.