For the vast number of weed seeds that we put into the chaff line only a few
are germinating so it's become the new low-cost option, the entry-level harvest
weed seed control option that growers can get into. In a lot of cases they're
just making something themselves and going for it, like they did with windrow
burning years ago.
What chaff lining is, is just taking all of the chaff off the sieve, putting a chute on the
back of the harvester to narrow that chaff down
and putting it in a narrow chaff line and putting the harvester back in the
same spot year after year, so we've got chaff line on chaff line on chaff line
and the straw is chopped and spread as normal.
When they put all the weed seeds into that chaff
weeds just don't really like germinating there, so we're getting
a lot of rotting and we're getting a lot of weeds just not growing. Chaff lining
can be used in conjunction with other tools, so it can be a lot of growers are
grazing the chaff lines. Once again it's anecdotal but they're really happy with
how the sheep are going on the chaff lines. We know that only about one to
three per cent of the ryegrass will survive passage through the rumen of the
sheep, so we know they're not spreading the seeds back out over the paddock too
much but they will probably make a mess of the chaff line itself and so it
remains to be seen how effective it is using chaff lining and grazing. Some
growers are using chaff lining in a lot of their crops and then perhaps thinking
right I want to get rid of that chaff line so maybe dumping a canola windrow on top
of there and burning a conventional windrow so that's another use. So combining
chaff lining with windrow burning looks to be a really great practice, whereas
other growers have said look we're getting so much rotting the chaff lines
aren't actually that weedy, we're quite happy we don't need to burn
a windrow on it.
Most growers are just making a chute
themselves, they're making it out of all sorts of things, whether it be three mil
plastic, one guy's made one out of a tarp, PVC tarp, steel is obviously very
common, all sorts of different things but a chute to just narrow down the chaff.
I guess some of the key things is, the opening sort of wants to be about 350 to
400mm at the bottom, we want to aim for a 200mm wide chaff line if we can.
What we find is if we have a 400mm wide opening that the material
follows the direction of the chute so even though it's 400mm wide at the
bottom of the chute we can still end up with it flowing down and ending up with
a 200mm wide chaff line. The other part of designing something yourself and
going and using chaff lining is the baffle and so the baffle is needed for
all of the chaff options - chaff cart, one of the mills, chaff on tramlines
chaff line - all of these things that just focus on the chaff. We're trying to get
the weed seeds to go below the baffle and into whatever we've got on the back
of the harvester and keep the straw above it, and we need to do that to make
sure we get the weed seeds where we're trying to get them to go. If we don't
have it there often we can get too many weed seeds escaping with the straw and
so that baffle design is where we really just have the sieve and we have a baffle
situated sort of here, maybe 350-400mm above the sieve and it can be sort of
either above the back of the sieve or sitting back a bit. There's so many
different options and the cost of chaff lining, it can be as simple as cheap as a
couple of hundred dollars to make your own chute and baffle or you can spend
three to five thousand dollars on a commercial one, so that's the cost of
getting into it. Then the only ongoing cost then is the nutrient concentration
into those chaff lines. We know that based on our figures that is roughly two
dollars or so per tonne of wheat grain harvested, so if you've got a two tonne crop
the cost of the nutrient concentration is about four bucks with chaff lining.
So it's really cheap. The overall cost to a farmer is anywhere in that sort of four
to seven dollars per hectare depending on yield of course.
It works on all systems but what we need is the harvester needs to be controlled traffic.
Essentially the harvester needs to go in the same spot every year and what a lot
of people have is just where the harvester is one-third the width of
the boom spray, so it's a compromised controlled traffic system and the other
part of it is that they don't block up. Growers are using tyne seeders with
no problems at all. We don't have to have a disc seeder, we do know that we can
get a shabby row of crop establishment when we put a tyne straight into that
pile of chaff. Just like the weeds don't like germinating, the crop
doesn't like it at all and that's probably one of the big negatives of
chaff lining.
We say to farmers are you happy with a strip of weeds that you can manage
or would you rather spread the weeds out and have them compete with
your crop. So putting them in a strip they can compete with each other and we
could maybe put extra herbicide there. Sometimes at harvest people just put a
little knife guard over the front of the harvester and don't harvest that little
bit of crop because it's full of weed seeds. So there are things that we can do.
Anecdotally the farmers are saying look they're really much cleaner than you
would think we must be getting a lot of rotting. The Esperance farmers that have
been doing it for a while, so when we get a wet summer we get a lot of rotting in
summer and then we end up with less weeds in the crop, whereas if we get a
dry summer we can get that strip of weeds in the crop.