TWENTY-FIVE hundred soil pits are testament to the zeal of Queensland researchers who are intent on showing northern region farmers how controlled-traffic (CT) farming can benefit their soils.
A swathe of 2,500 pits from Narrabri and Walgett in NSW to Moranbah in central Queensland have been laid bare for all to see the relative condition of soils under controlled-traffic and conventional farming systems.
And the message is clear - soil between the controlled-traffic tramlines is in excellent condition.
Queensland Department of Natural Resources and Mines Principal Soil Scientist Des McGarry led field day participants in a recent inspection of soil pits on two adjoining farms 30 km east of Dysart.
Two of the pits were in recently harvested sorghum paddocks immediately across the fence from each other - one on a controlled-traffic, zero-till farm and the other on a conventionally tilled farm. Soil structure in the controlled-traffic field was excellent between the permanent wheel tracks and compacted to 30 cm (12 inches) in the tracks.
"This is exactly the sort of result we saw across 35 controlled-traffic grain farms in January this year," said Dr McGarry. "It puts to rest an early report of compaction between the tramlines on CT farms. There were sporadic wheel marks from planters and spray rigs between the tramlines in some fields, but in general the soil structure was in excellent condition. Just like never-farmed soil."
In the conventionally farmed paddock at Dysart, the worst soil compaction went down to 60 cm, which Dr McGarry said seemed to be linked to the duals on the big tractors. The plant roots could be seen to get around the big blocks of soil, "but maybe they had to work harder than in the CT soil through the fence".
"What we are trying to achieve is maximum yet sustainable use of the land in a risk-free, low-cost farming system for growing grains. We want to better guarantee harvests, year after year. We want to make sure the soil structure is so good that every drop of water gets into the soil and the plants can suck every drop back out! We want to make the soil structure better for future generations.
"Both CT and conventional grain farming systems can give good yields. But the risk and the costs are less in the controlled-traffic system. There is no one answer. We can all learn from each other and get a system that works best for each grower on their own property."
Dr McGarry 's team is also measuring water infiltration in both conventional and controlled-traffic paddocks and plans to report findings to future field days.
Program 3.4.1 Contact: Dr Des McGarry 07 3896 9477
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