Trials assess moisture gain from claying and spading

Key points

  • The Millsteed family has been testing different soil amelioration methods to improve yields on non-wetting soils
  • Spading produces a 0.5-tonnes-per-hectare yield advantage
  • In 2014, the Millsteeds tested a deep digger to explore if it can be used to incorporate clay to a depth of up to 500 millimetres and bring clay to the surface
  • The deep digger produced a 1t/ha yield advantage in lupins 
Photo of man kneeling in deep ripped versus clay-based paddock

Brad Millsteed on his Watheroo property. The land on the right has been spread with a clay-based topsoil and the land on the left has been deep ripped. Brad is conducting his own trial to see the results.

PHOTO: Evan Collis

Facing a worsening situation with non-wetting soils, Brad Millsteed has been testing the full range of soil amelioration methods – spading, claying and delving – on his family’s 3600-hectare mixed-farming property near Watheroo, Western Australia.

Brad, who farms with his wife Denise, parents Jeff and Tina, uncle Brent, aunt Jan, and cousin Adam and his wife Karina, says they have more non-wetting soils now than ever before.

For the yellow sandy soils, which over time have become grey and non-wetting, the Millsteeds are testing spading, claying and delving.

Spader trial

The Millsteeds implemented a trial to test spading in March 2013. A contractor was hired to spade 45ha. To prepare for the trial, the Millsteeds deep ripped the ground before the contractor spaded the soil to 400 millimetres.


Growers: Jeff, Tina, Brent, Jan, Brad, Denise, Adam and Karina Millsteed
Location: Watheroo, Western Australia
Farm size: 3600 hectares (3100ha arable, 1600ha cropped)
Rainfall: 363 millimetres (20-year annual average), 277mm (20-year growing-season average); 348mm (10-year annual average), 259mm (10-year growing-season average)
Soil types: sand to clay
Soil pH (topsoil average): 5.5 (calcium chloride)
Enterprises: cropping, 1600 Merinos ewes and 50 Poll Herefords
Typical crop rotation: wheat/lupins/wheat
on sandplain; wheat/wheat or wheat/canola/wheat on heavy country; at least two seasons of pasture following crop on all soil types

After spading, the ground was flattened using a tyre roller. Brad knows that some people like to leave ridges to limit wind erosion, but he says this has not been an issue for them and flattening enables more accurate seeding.

Nonetheless, he was not satisfied with the initial tyre roller. He has since looked at a roller that a neighbour imported from Canada and was impressed with the job it did flattening the soil.

Mace wheat was the first crop grown on the treated area and it yielded 0.5 tonnes/ha more than wheat on the unspaded treatment.

One reason for the higher yields, he says, is because crop roots in the spaded country penetrated the soil deeper in search of moisture and nutrients.

“Over summer when I was collecting soil samples to a depth of 30 centimetres, the amount of smaller roots in the spaded area was phenomenal compared with the unspaded soil,” he says.

Although Brad was pleased with the yield increase, he was wary about relying on contractors at such an important time of the year, even though he can see and appreciate the benefits of spading.

“However, it’s expensive at $200/ha and I wonder if we need to work even deeper than what’s possible with spading or mouldboard ploughing to enable plant roots to access nutrients and water from deeper within the soil profile.”

In 2013, with wheat prices at $320/t and favourable seasonal conditions, Brad says the spading was basically paid for in one year. In less favourable seasons and at lower grain prices, he estimates two years would be needed to recoup the cost.

In 2014, lupins planted on the area spaded in 2013 produced a 0.5t/ha yield advantage.

The Millsteeds will check the yield difference again this harvest using yield-mapping technology, available through a header upgrade.

Claying trial

Also in 2013, the Millsteeds trialled clay spreading using four different treatments:

  • grey clay dug from depth;
  • clay from the side of a deep drain;
  • gravel from a gravel pit; and
  • yellow sand from the side of a deep drain.

The clay was applied at two rates (150t/ha and 300t/ha) using a muck spreader.

On the first 50 metres of the trial, the clay was left unincorporated, on the second 50m the soil was ripped and the clay spaded. The remainder of the trial was deep ripped only.

The muck spreader was hired for $300 per day; additional costs were tractor, operator and clay extraction costs.

Overall in 2013, Brad says claying increased wheat yield by 1t/ha and incorporating clay into the soil proved paramount. In 2014, it produced a visual difference in crop growth, which went on to produce a yield difference at harvest although he did not quantify the difference at the time.

In addition to the cost, Brad also found logistics had a big impact on the economics, with the clay source needing to be as close as possible to the site being treated.

This year, the Millsteeds have been recording crop growth data through the season to see if there is a visual difference between the areas using an unmanned aerial vehicle (UAV). The UAV is capturing information using different types of sensors (or cameras).

Beating compaction

In January 2014, the Millsteeds set up a 5ha trial to test a Grizzly deep digger’s ability to dig the soil and incorporate 150t/ha of clay taken from the side of a deep drain.

After using the digger, Brad says clay was incorporated through the profile. In the untreated area the clay remained on the surface.

The digger was also used to bring clay up to the surface. In the unclayed area, the Millsteeds were able to delve clay and bring it to within 25mm of the surface.

“The digger is less than half the cost of a spader,” Brad says. With further tests, he says he may be comfortable buying a digger because he wouldn’t need to upgrade the tractor.

He says the digger enables soil to be cultivated to a depth of up to 500mm – deeper than spading or mouldboard ploughing, which works no deeper than 400mm.

Brad was impressed with the optional multi-slat crumble rolling system at the back of the digger: “The soil was extremely dry and without the leveller we would have had football-sized clumps of soil on the surface.”

He says sowing Coromup lupins at 80 kilograms/ha on 5 May into soil that had been clayed, incorporated and levelled was “a piece of cake” compared with the spaded country as the crop was sown without parallelogram seeding boots. The seeding depth on the spaded country tended to be variable, leading to uneven emergence.

By August 2014 there was no visual difference between the lupins sown into the clayed soil that had been incorporated with the digger or the spader. However, at harvest, the Millsteeds measured a 1t/ha yield advantage on the area treated with the digger.

Brad was excited by the results and is keen to try the digger again when conditions and time allow.

More information:

Brad Millsteed,
0429 008 750,,




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