Innovative ploughing method stands up to sand
GroundCover™ Issue: 136 September – October 2018 | Author: Quinton McCallum
Previously unproductive sandy soils at Meningie in South Australia’s Upper South East are enjoying new life thanks to a method known as Plozza ploughing.
Non-wetting sands have been a major challenge for growers around Meningie, according to Platinum Ag Services agronomist Matt Howell.
“Our problem soil types are mainly sands and sandy loams,” Mr Howell says. “They are quite coarse and they become non-wetting very easily. We have sand that does not get wet until the middle of July. When it does rain, it takes 100 millimetres of rainfall for it to wet up even slightly so we can get a crop out of the ground.”
While on a study tour in Western Australia in 2015, Mr Howell discovered the positive effect Plozza plough discs had on ameliorating sandy soils and he has employed the idea in his region.
The first Plozza discs – named after designers Ben and Sean Plozza – were brought into SA in 2017 and used in broadscale trials on two local farms.
After showing the method and results to local grower groups, several more farmers – some in the Upper South East and two on the Eyre Peninsula – bought discs and built their own Plozza ploughs.
The special 750-millimetre discs, which are deeper than conventional plough discs, are fitted to an old one-way plough with every second jump arm taken off to create wider spacing.
“The only unique thing about the plough is the discs,” Mr Howell says. “The discs come in, they fit to your standard hubs, the holes are drilled out to fit the different types of ploughs and we can fit them straight to a conventional machine.”
He says the hydraulic pressure is increased to get more downforce and hold them straight in the ground. “As it’s digging, it shoots the sand up across the face of the disc and basically inverts it,” he says. “You are flipping that topsoil to the bottom as much as possible.
“It is not perfect but it has the ability to break out the properties of soils, and also has the ability to get down to about 300 to 350mm deep and break up a soil compaction layer at the same time.
“The Plozza plough is a compromise of the offset disc one-way plough and the mouldboard plough, but it tends to get deeper.”
He says mouldboard ploughing and spading have been tried in the district but they were ineffective due to their inability to handle rocky country.
Along with its ability to deal with rocks, in farmer-scale trials the Plozza ploughing method has shown significant benefits for crop yields and soil health.
“We have conservatively said we can improve yields by over half a tonne per hectare in cereals, no worries,” Mr Howell says. “This year it is going to be more than that, purely because of the better crop establishment. With such a dry start our non-wetting sands were still not out of the ground in July, whereas all the Plozza plough country was all up and growing happily.”
As well as improved establishment and yields, Mr Howell says the Plozza method has also improved soil health and root depth. “The soils are looking considerably healthier because we are dealing with multiple problems in one pass,” he says.
“Not only are we dealing with non-wetting sands, we are dealing with soil compaction at the same time because we are breaking up that hardpan layer down at about 220mm below the soil surface – the old tilling depth – and we’re basically doubling the bucket size that the cereal has access to by getting rid of that hardpan.
“As soon as we can establish a cereal we can grow more root matter as well, so we are finding we are getting a deeper rooting depth and better water utilisation.”
GRDC-funded trials in WA that examined different soil-amelioration methods including spading, mouldboard ploughing, deep ploughing and the one-way Plozza plough showed that all treatments had similar yield results and similar improvements in reducing soil water-repellence, but the Plozza plough was a clear winner when it came to profit per hectare.
A combination of deep ripping and spading had a profit margin of $146 per hectare, while the Plozza plough’s profit margin was $220/ha. The Plozza plough also showed an 85 per cent reduction in soil water-repellence, which was on par with the mouldboard plough.
As well as its ability to improve the yield potential and health of non-wetting sands, the Plozza ploughing method’s major incentive is its low cost.
“One-way ploughs are quite a common old-school piece of machinery which are rotting away in the back of yards now that we have gone away from conventional tillage, so there are plenty of these things lying around,” Mr Howell says.
“Depending on how much the plough costs, one can be set up for between $5000 and $7000, including the discs. To get a similar mouldboard plough would cost between $70,000 and $80,000.”
He says the Plozza plough does not suit every situation and is not the answer to every sandy soil constraint, but it is good for his region’s sands, which are in cropping areas surrounded by lime and limestone.
“If we can turn this land from what has basically been dead-loss country in the past to breaking even or making a slight profit, we are miles ahead because we are not dealing with pure financial loss any more,” he says.
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