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 1