GCTV Ep#12 Mouldboard Ploughing
Narrator: Debra Bishop An age-old practice making a modern day comeback.
Mouldboard ploughing was first used centuries ago.
A 30-centimetre layer of soil is turned to become topsoil.
Weeds, weed seed and non-wetting soil are all buried.
Subsoil, often containing clay and less water resistant, is brought to the top.
A spread of lime helps restore soil pH.
Grower Stuart Smart is a convert.
Stuart Smart: Grain Grower Mingenew, WA It really is huge and it is quite hard to
fathom sometimes.
Narrator: At Mingenew south east of Geraldton in Western
Australian, Stuart’s family has worked this sand plain land for generations.
22 thousand hectares almost all of it arable and producing a bumper crop.
Stuart Smart: This year is a very good season for us we
will do above average for sure so I would expect to see probably 600 kilos difference
this year.
Narrator: That difference, says Stuart is largely thanks
to mould board ploughing.
Stuart Smart: The mouldboarding no doubt has probably increased
our yields at a minimum of 10 percent but in some stages we’re seeing a 30, 40 percent
increase in yields just because we do not have that weed competition anymore and we
are also getting major benefits from turning that soil over with mineralisation of nutrient
and fertiliser that we could never have taken before in that non wetting band.
To date we have actually mouldboarded nine thousand hectares.
The plan is to only turn it once every 10 years.
Narrator: This is Stuart’s 3rd mould board plough
his first purchased back in 2010.
Since then the yields have increased and the weeds have reduced.
But mould board ploughing is not for everyone.
Stuart Smart: I have had a lot of people say it is really
anti what we have been trying to do you are turning the soil upside down in an era of
no till is not really on.
Narrator: Science too is cautious.
Peter Newman: Australian Herbicide Resistance Initiative
The results are not consistent everywhere so the real trick to mouldboard ploughing
is to find the right situation for it.
So on our non-wetting sandy soils with herbicide resistant weeds and acid subsoils fantastic
fit however there are situations where you do not want to mouldboard plough because you
may be bring up soils that has characteristics that you don’t want perhaps boron toxicity
or really sticky clay or something like that so there is certainly finding the right situation
is the key to its success.
Narrator: Stuart’s ploughs are now packed away, awaiting
next season’s workload.
Stuart Smart: Our aim each year now now we have got two
ploughs is to do a minimum three thousand hectares a year.
Narrator: Costing up to 180 thousand dollars these machines
are a carefully considered investment and require a modified seeder.
Stuart Smart: You do need to have a proper seeding unit
for it you cannot go in with a conventional bar, they are too heavy and they sink your
seed placement is shot and so you need to go with something that is very light weight
and will just give it that firming pack that it requires.
So we have gone a couple of different ways, in the first year we tried the air-hoe drills
and that did not work.
We went to coil packing in front and then the air-hoe drill and that did not work so
we then went to the coil packer with a little seeding boot called an Agmor boot made in
WA here and it is a plastic type of boot and it basically just bends backwards and forwards
and sows it at about 10 to 15 mil which is pretty perfect.
Narrator: Erosion though, is a serious risk unless soil
inversion and sowing are done the same day.
As with all tillage practises timing is the key.
And in the days before no till farming systems, erosion was one of farming’s biggest problems.
Right now, Stuart’s investment around 70 dollars a hectare, is paying off for him.
Stuart Smart: It’s cheaper than the spray and we can correct
a paddock in one year which would take us five maybe eight years with chemical trying
to do that same thing and we’d never been able to tackle the non-wetting side of it,
chemical would never fix that.
Narrator: Certainly that’s the case now, however GRDC
is investing in research to correct non-wetting soils through chemical application.
But questions remain about the use of mouldboarding because research, unlike the practice, is
quite new.
Peter Newman: If we talk about non wetting soil we know
soil is non-wetting because it has wax coating the sand grains and we’re burying that and
bringing up wettable soil which is great in the short term.
We’re concerned that perhaps it will stay non-wetting at depth for a long time.
Theory and research tells us so far we think the microbes, the bugs, the bacteria will
eat that wax off that soil in time but we can’t say that with confidence now.
Burying weeds seeds, we know for some of the grass particularly rye grass that for that
seed that we bury will rot in just a couple of years.
We know that for wild radish there’s some work done that shows that it can last longer
when it’s placed at depth and that there may be a few percent of weed seed left in
10 years time if we bring them back up.
Narrator: Also, some export markets are sensitive to
large carbon footprints, and fuel-hungry mouldboard ploughs are certainly that.
Peter Newman: The good news is that we are only doing it
every 10 or 15 or even 20 years and some growers say they want to do it once and then they
want to sell the thing and that is it.
So it does have a big carbon footprint but we should be able to average that out over
10 years or so.
Growers that are thinking about getting into mouldboard ploughing, the first thing they
need to do is understand what is in their subsoil and they need to understand is that
going to be a subsoil that you want to bring up.
And they need to work with soil scientists and their agronomists and then the first thing
to do really is to trial it on their farm if it hasn’t been done in their district.
Narrator: For grower Stuart Smart there is no turning
back this practice from the past is firmly a part of his future.
Ends
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