[MUSIC PLAYING]
DAVID PANNELL: Today, we're out in the wheatbelt
of Western Australia near the town of Merredin,
and I'm speaking to Greg Shea who's
a development officer with the West Australian
Department of Agriculture and Food.
Welcome, Greg.
GREG SHEA: Great to be here, Dave.
DAVID PANNELL: So we're going to talk about soil acidity, which
is a big problem in the wheat part of Western Australia.
So can you tell us a bit about what's behind soil acidity?
What causes it?
GREG SHEA: Well, really, it's the result of agriculture.
Over time, the long-term effect is
that there's an imbalance in the system,
and the soils start having their chemistry changed.
And the result is that the roots of the crop
are compromised by the soil acidity.
DAVID PANNELL: OK.
So what sorts of farming actions cause it?
Fertilizer application?
GREG SHEA: Mainly nitrogen-- and use of legumes over time
and also leaching of nitrogen.
So it's an imbalance that happens in the soil--
as well as the export of any agricultural commodity
from a farm.
So over time, that just creates the imbalance.
DAVID PANNELL: And how widespread
is it in Western Australia?
GREG SHEA: It is very widespread in Western Australia.
We've got millions of hectares affected.
And a lot of soil has got a problem
in terms of subsurface acidity.
That's where it expresses itself.
So crops really do have a problem filling the grain
at the end of the season as a result of the soil acidity
problem.
DAVID PANNELL: So the result's lower yields?
GREG SHEA: Absolutely.
Yes, and quality.
And so it's just a major factor in crop production.
DAVID PANNELL: How much lower yields are we talking?
GREG SHEA: Well, if we ameliorate the soil acidity,
then we can get responses of 10% to 40%.
It depends on the seasonal conditions.
DAVID PANNELL: So what are the options
that farmers have to try and manage it?
To try and reduce these impacts?
GREG SHEA: Well the main one is to bring the use of lime
into the farming system.
And that is a product which-- when it reacts with the soil--
reverses the effects that have happened over time,
and the soil acidity is reduced.
It does take time to actually work,
but that is the main thing that we get the growers to use.
DAVID PANNELL: So they're applying lime-- a bit
like a fertilizer?
GREG SHEA: Absolutely like a fertilizer.
Yes, they do.
And it's something that's been promoted for many years.
But growers have been hesitant in some cases
because it's usually cheap to buy,
but the transport cost is often the major factor.
DAVID PANNELL: OK.
So how about the economics then over all?
Do the economics of applying lime
stack up in certain situations or not?
GREG SHEA: Well, it's a really tough one
in the lower rainfall areas, David,
because the yield potentials aren't as high.
We often have more drought, and so the effects of soil acidity
are worse because, as I say, it's
working about the roots are affected.
And obviously, there's a long way from the sources of lime--
usually, crushed limestone or lime sand.
So there is a big question for the farmers.
It's only in the last few years that the tonnage
of lime to use in the wheatbelt has kicked up in amount.
DAVID PANNELL: I imagine that when you're applying lime,
you're bearing a cost up front and then there's
benefits for carrying down the track.
GREG SHEA: Yes.
DAVID PANNELL: So that could also
be a factor that farmers are considering?
GREG SHEA: It's the big factor.
Apart from circumstances which are relatively rare
and which we're still investigating,
the general experience is it's four
or five years until the actual lime is exerting its effect
and the crop yields start improving.
So it's that delay that is really crucial in why the take
up of lime by farmers is restricted.
Because they see it as something where the budget is often
under stress, and it's the first thing that gets
knocked off the list.
DAVID PANNELL: Right.
Right.
So what's the Department of Agriculture and Food
doing in terms of research or extension
to try and address the acidity problem?
GREG SHEA: Well, it's in all areas, actually, David.
And the main thing is getting growers
to make sure they make the correct decisions about which
kind of lime source they use for their farm-- depending where
their farm is relative to where the sources of lime are,
liming agents.
And also just a planning process in terms
of working out where the resources should be allocated
on the farm-- between fertilizers and lime.
Because often we find that once liming is taken up
and the soils are improved, particularly phosphate
fertilizers, you can actually use lower amounts of phosphate
because that correction that's happening in the soil.
So there are savings to be made.
And also just putting together where the paddocks are located
on the farm where the biggest responses to lime will occur.
So it's targeted lime.
It's not one time of lime over the whole farm.
It's more like 2 and 1/2 or 3 tons of lime--
DAVID PANNELL: Per hectare.
GREG SHEA: --per hectare-- on the areas
which are most likely to be responsive quickest
so that economic issue is dealt with.
DAVID PANNELL: So can you explain a bit more
about the phosphorus story?
You mentioned that they might be able to cut back
on their phosphorus application?
How does that work?
GREG SHEA: Well, the background to it
is-- I haven't mentioned before because I
was talking about soil acidity.
But the actual effect in the soil
is that aluminium becomes more available in the soil
as a result of soil acidity.
DAVID PANNELL: And aluminium is toxic to plants.
GREG SHEA: Aluminium is toxic to plants.
So most plants that we grow don't like aluminium
in the soil solution.
And so the end result is the roots
are restricted in their growth, and therefore, they
can't explore the soil for the reserves of phosphate
which have built up over the years.
And so therefore in those situations,
you're generally putting on phosphate
to meet the plant's requirements.
So once it's sorted out, with liming and the soil
acidity becoming less of a problem,
then that action is reversed.
And it's not so responsive to applied p,
because they're already getting it from the soil.
DAVID PANNELL: OK.
Thanks, Greg.
That's been very interesting.
GREG SHEA: Thanks, David.
It's been great talking to you.
Professor David Pannell, BSc(Agric), BEc, PhDUWA School of Agriculture and Environment
Jacob Hawkins, BA(Biol), MESM, PhDSchool of Agricultural and Resource Economics
