Spending on sandplain soils can pay off

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Photo of Stephen Davies
DPIRD soils researcher Stephen Davies is undertaking research with GRDC investment into the impact of subsoil mixing and deep-tillage practices on sandplain soils. PHOTO: agVivo

New research is shedding light on crop yield performance and soil improvements following a range of inversion and deep-tillage tactics on Western Australian sandplain soils. This will help growers make investment decisions about overcoming the soil constraints of compaction, water repellence and acidity on their property.

Better understanding the impact of subsoil mixing and deep-tillage practices on sandplain soils is a high research priority for the GRDC’s Kwinana West Port Zone and Albany Port Zone Regional Cropping Solutions Network (RCSN) members.

Trials addressing this issue were set up at Goomalling (yellow sandplain) in 2017, with GRDC investment, and coordinated by agVivo Pty Ltd farm consultant Tim Boyes, with input from Map IQ’s Joel Andrew.

Trials were also conducted at Meckering (pale sand over gravel) by Department of Primary Industries and Regional Development (DPIRD) soils researcher Dr Stephen Davies, with GRDC investment, in 2016 and 2017, and with input from DPIRD economist Dr Elizabeth Petersen.

Both sites were managed by the cooperating growers and results showed yield benefits were worth the investment in amelioration tactics.

Average grain-yield increases from inversion and deep-tillage soil-amelioration practices ranged from:

  • 26 to 50 per cent (2016 at Meckering)
  • 5 to 39 per cent (2017 at Meckering) and
  • 2 to 93 per cent (2017 at Goomalling).

Dr Davies says the key to success is removing subsoil compaction in the first year to boost crop root access to deep soil moisture and increase plant uptake of water and nutrients (such as potassium and nitrogen) from deeper in the profile.

He says removal of topsoil water repellence and undertaking deeper soil mixing, such as by using spading or inversion with a one-way or mouldboard plough, appears to be important for longer-term, sustained yield responses.

“The most profitable treatment at the Meckering site in 2016 and 2017 was one-way ploughing, followed by ripping with spading and soil inversion (using a mouldboard plough),” he says.

“Only very deep-ripping (with or without topsoil inclusion) or using one-way ploughing with deep-ripping were profitable in 2017 at Goomalling.

“The removal of deep compaction in the dry season of 2017 improved root access to subsoil moisture, which boosted grain yields compared to no treatment.”

Dr Davies says economic analysis of the inversion and deep-tillage systems found cost recovery from most tactics could be achieved within two years, except for delving and delving plus spading, which have a higher initial implementation cost. “Many treatments achieved cost recovery in the first year, although this depended on the site,” he says.

Dr Davies says these research projects provide valuable insights into the complexities of managing deeper soil profiles and the potential gains from tapping into moisture and nutrients below a depth of 50 centimetres.

“This work will help to develop more comprehensive agronomic packages and assist consultants and growers to make more-informed decisions to optimise the benefits and investments in undertaking soil manipulation to depth,” he says.

DPIRD is continuing field trials in 2018 as part of a suite of soil-manipulation research projects with GRDC investments across the WA grainbelt, through the GRDC’s Soil Constraints West initiative.

GRDC Research Codes DAW00244, AVP00003-A

More information:

Dr Stephen Davies
0408 439 497, 08 9956 8515
stephen.davies@dpird.wa.gov.au

Useful resources

Goomalling and Meckering trial results update paper

GRDC Replacing Machinery: Kwinana West booklet