WA's sand plain soils feature multiple constraints including water repellents
acidity and compaction. All focus points of GRDC's 33 million dollar investment
in the Soil Constraints West project. After five dedicated years the projects
drawing to a close with key outcomes emerging for growers.
At Goomalling where the deep yellow sands are water repellent the project has compared
strategic deep tillage options to ameliorate these types of soils.
This is a mouldboard plow treatment, you can see here where the top soils been turned in and a small
layer of subsoil being brought up on top. Knowing your constraints is the first step.
Really understand your soils beforehand so do a lot of soil testing
understand the constraints and the fertility of the soil and what the soil
profiles actually like to try and almost understand the water holding capacity of
that soil. The project is developing sustainable soil management practices
most of the research has been done in the West but the findings are also
relevant to Australia's southern cropping region. The interactions looks
very similar in the first year significantly improved biomass and
significantly improved tiller counts.
On this site Steve Davies has worked closely with agronomist Tim Boyes to determine deep
tillage soil options to tackle water repellence. So we've got deep ripping
which is really about loosening the soil and breaking up the compaction but it
doesn't really greatly change the nature of the top soil. Then we've got tools
which are really looking at deep soil mixing so they're actually more
thoroughly mixing that soil down to 40 centimetres and then we've got some
ploughing options which allow us to invert the soil and that actually really
buries the topsoil and brings up a layer of subsoil. What we end up finding is
that we've got a fair few roots growing through here
and then we can as we go down just to start to see some roots growing deeper into
that profile. Soil constraints result in lost grain production worth more than
four billion dollars annually just in WA. A key project outcome is that growers
should consider treating multiple constraints over smaller areas rather
than working on one constraint at a time. Techniques that work on multiple
constraints can lead to greater benefits overall. We've got an untreated control
plot here and then a mouldboard plough plot here and really the obvious differences
are this has got a lot of small heads in it and really with the water repellence
a lot of these plants have come up late and a small and it's got a lot of weeds
in between the crop rows. If we look here at the mouldboard plough one, we've got these
bigger heads obviously healthier plants and in between the crop rows it's really
clean there's no weeds. The project has extended its work beyond the field with
a team of PhD students, Australia's next generation of researchers who are
providing innovative project information. They're really doing some basic
fundamental research on understanding soil water repellence and the molecular
interactions which will potentially give us a better insight into how to manage
the problem and also looking at how soil water repellence interacts with crop nutrition.
In areas of quite high water repellence soil inversion techniques
or deeper mixing potentially can change the soil surface and reduce repellence.
What we're finding with the soil amelioration treatments is that with deep
ripping we're removing that deeper compaction and that's giving us better
access to subsoil moisture on these deep sands but there are other options
that growers if they don't quite ready to go down that step they can use things
like soil wetting agents and even on row sowing is proving to actually be quite
an effective and consistent way of managing the problem.
Steve says whatever options growers choose there's a formula to follow. Firstly to really understand
the soils they're actually going to ameliorate secondly they really need to
actually work on the paddock after they've done the amelioration effort and
actually sort of prepare the paddock and get it ready for seeding.
Thirdly they actually need to sort of you know ideally have a controlled
traffic farming system in place so they're not actually recreating that
compaction that they've actually just got rid of as part of the soil
amelioration practices and they need to have a strategy for how they're going to
seed these ameliorated soils because the soil is very soft.
The project has developed resources to help growers understand where amelioration
strategies fit including how to choose the most cost effective practices.
We've got the tool ranking options for soil amelioration which is a financial
comparison tool. There's also the CTF calculator for looking at the benefits
of CTF-ing systems and also some ebooks they've been produced and currently in
production as well that are looking at you know providing some of the detailed
information behind these constraints and how to manage them.
The cost to determine and apply the options is around forty one dollars a hectare but there are
tangible returns for the time the effort and the outlay. What we're finding with
these options is that generally they're really profitable and that we find that
within the first year or two you actually pay for the cost of doing the
treatment and then you basically it's profitable from then on.