Modified ripper treats acidic subsoils
GroundCover™ Issue: 126 | Author: Nicole Baxter
Although Western Australian grower Brian McAlpine has spread lime on his soils for more than 20 years, a recent nutrient analysis showed the ameliorant was not moving into the subsoil as he had hoped.
Brian, who farms with his wife Tracy near Latham, about 320 kilometres north-east of Perth, says the nutrient analysis shows topsoil pH is conducive to growing crops at about 6.0 (calcium chloride), but a pH of 4.7 (calcium chloride) in the subsoil is constraining root growth.
He investigated mouldboard ploughing and spading to push lime into the subsoil, but their cost and practicality did not make them viable options.
Brian first heard about the GRDC-supported deep-ripping and topsoil inclusion research two years ago when he attended the Liebe Group’s annual field day.
Although he was excited by the concept, it was not until he attended the Yuna GRDC Crop Update in 2015 that he could see how growers were adding manufactured topsoil inclusion plates to deep-ripping tynes and making them work on a commercial scale.
He saw the concept as simple and cost-effective because he was able to modify his existing deep-ripper.
Brian uses a 447-kilowatt tractor to pull a 6.7-metre deep-ripper fitted with topsoil inclusion plates. The distance between the plates is 150 millimetres, which holds the soil open long enough for ameliorated topsoil to drop into the subsoil.
Last year he used the ripper fitted with topsoil inclusion plates across almost 2000 hectares. He is assessing the impact of the work and is yet to make a decision about ameliorating his remaining 4500ha.
“The benefit of deep-ripping with topsoil inclusion plates is we’re tackling two issues at once: subsoil compaction and subsoil acidity,” Brian says.
“All we’re doing is increasing the size of the moisture bucket, which will enable crops to access more water from deeper in the soil if we have a dry September.”
To growers thinking of trying deep-ripping with topsoil inclusion plates, Brian says that success depends on doing the work at the right time.
“You must have good subsoil moisture and a dry topsoil, which is what we had in 2016,” he says. “So it’s not something you can do every year.”
Brian’s ripping tynes are spaced at 457mm intervals. He rips each paddock at one degree offset from the direction of sowing to enable seed to be placed at the correct depth.
The next time the paddock is ripped he plans to work the soil at one degree in the opposite direction.
Coil packers are pulled behind the ripper, working at five to six kilometres an hour, to smooth the seedbed.
Brian has also adopted a 13.1m controlled-traffic farming system to isolate the compaction and preserve his deep-ripping and topsoil incorporation investment.
More information:Brian McAlpine,
0428 642 051,