What looks like the start of an open cut mine is in fact one of three major soil-focussed
projects being run by Western Australia s Department of Primary Industries and Regional
Development as part of a $42 Million co-investment with the Grains Research and Development Corporation.
This trial site is 300 kilometres southeast of Perth at Tarin Rock.
This GRDC DPIRD investment s about achieving maximum yield potential through what s theoretically
possible to re-engineer soils.
Its re-engineering soils on an ambitious scale because these heavy duty machines are excavating
to a depth of 80cm. That s 200 to 300mm deeper than most soil
amelioration machinery can work and that s where the theory comes into it.
Where you are trying to re-engineer depth of soil and try to give more access to plant
roots to the untapped subsoil water and nutrient.
To allow that access, the top 80cm of soil is peeled back in layers. Put aside to be
treated with ameliorants, then backfilled.
We are bringing actually only 10cm at a time and mixing with different ameliorants for
example compost and gypsum and lime and also some cases some nutrient because we are using
compost to compensate on those treatments as an inorganic source of nutrient.
At this site there are shallow duplex soils with a thin layer of sand on top, creating
a non-wetting barrier. Another constraint is acidity though the top 30cms.
Below that there s a grey sodic zone which has poor cation exchange capacity and is prone
to waterlogging, creating challenges for plant root development and nutrient uptake.
Lower down the profile are good yellow clays. Across Western Australia there are 12 million
hectares of soils such as this.
On this soil type the main issues are the water doesn t infiltrate or it takes a long
time to infiltrate so in a year like this you ll see at depth it s still reasonably
dry but the top is waterlogged and then at the end of the year we ve got moisture 400mls
down that we can t access so the crop runs out of moisture but it s as wet as at depth
so we want to try to use that moisture later in the year if we can.
Mark Peace is a committee member of GRDC s Soil Constraints West project.
A state component of a multi-agency national research program that has been running since
2015. Its aim is to find solutions for those major
soil constraints which stop growers such as Mark from maximising crop returns.
This investment has been on the back of 5 years worth of single constraints, we call
them Soils Constraints West series 1 projects we were looking at individual constraints
across the entire state. And this investment leads through by pulling that altogether and
making the next quantum leap.
A leap, that for Gaus Azam and his team has meant they have to dig deep.
That will allow plants to grow into that subsoil where there s a lot of moisture and plants
never use it and there s also a lot of nutrient in this type of soil like lots of potassium
and plants never use it and so we re trying to explore that and hopefully get some bangs
for the bucks.
Bangs, such as maximising potential yields.
Yes so at this site we are trying to achieve maximum yield what is theoretically possible
with no yield constraints at this site and all sites.
An earlier project led by Dr Azam involved similar re-engineering of the soil to remove
compaction and acidity. While not going as deep as the excavation here, that trial produced
impressive results.
In 2018 where in a controlled situation we had like 1.4t of wheat but in a 45cm re-engineered
we grew 3 and a half tonne of wheat.
Encouraging as those results might be there s reason to remain cautious. Lessons learnt
from the Soil Constraints West projects need to be factored in. Those trials revealed
in certain situations or locations amelioration had contributed to poor crop establishment
and erosion.
If you go north wind blows 60 kilometres rather, per hour so it can do wind erosion.
Perhaps the biggest obstacle looks like this. Can excavation to this depth be replicated
on a paddock scale using machinery more commonly found on farm.
You can see deep ripping machine now that can go 800mm. You can see delver that can
go 1 metre even some cases more than a metre. That can bring those beautiful clay on top
if we can demonstrate that it has value in it they will build a machine.
Grower Mark Pearce agrees
If we can get the yields if we can see an extra tonne to the hectare it will happen,
we ll make it work somehow. The shallow rippers are doing now 5 to 600, we ll make a start.
The next 200, well machinery companies if they can make money out of it, it will happen
they ll build the machine.
What GRDC s Rowan Maddern would like this blue-sky project to lead to, is solutions
that growers can economically apply.
if the project proves the cost benefit growers will be able to apply some of the findings
from these sites in all their paddocks.
There are other questions to be answered. How quickly can you get back on these re-engineered
soils, what crops should be sown? These questions and more are being investigated
by 2 other major soil projects that are part of the $42M co-investment.
While it might look like a construction site now, barley will be sown when the re-engineered
soil is put back and Mark Pearce is anticipating a good result.
It will be a bit later than the rest of the crop it will be a bit behind but we re hoping
at the end of the season its going to hang on a lot longer than the rest of the paddock.
I hope its going to tiller more as well it s going to have more access to the deeper
nutrients, potash and everything at a lower level and yeah hopefully yeah more yield due
to more plant available water.
It s a hope everyone here would share because it would also indicate the multimillion-dollar
research investment is on the right track.
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