Western Australian researchers are investigating herbicide options and new crop technologies
to boost profits from strategic spray fallows in low rainfall areas.
If successful, improved fallows could increase the subsequent wheat crop yields by up to
one tonne per hectare and canola yields by up to half a tonne per hectare, as well as
cut herbicide costs by as much as $50 per hectare on some soil types.
This would be driven by conserving valuable soil moisture and nutrients and achieving
effective weed control from one season to the next, according to agronomist Bernie Quade,
of Quade AgriServices Landmark. He is coordinating a spray fallow trial site
at Wyalkatchem that is funded by the Grains Research and Development Corporation’s Regional
Cropping Solutions Network. “For this part of the world where we are
limited by yield by water, I think it is very difficult to make a profit off every paddock
in every year. So the concept behind it is trying to preserve some of the water from
year one and don’t grow a crop, keep it clean and carry it over to the following year
to make a profitable crop. You can get multiple germinations of weeds in that fallow period
to drop weed numbers in that paddock. And the other one would be nutrition. We can,
particularly on the loamier heavier soil types with higher organic carbon levels, we can
mineralise a significant amount of nitrogen.” The Wyalkatchem trial and other GRDC-RCSN
trials at Mingenew and Mullewa run by Crop Circle Consulting, are looking at the effectiveness
of summer and winter weed control from residual herbicides and the tolerance of new crop technologies
to these herbicide treatments. “If we can find out which of these residual
herbicides can fit to a certain crop type the following year, then we can maybe put
a package together for different farmers as to which is the best residual herbicide to
use. There is two parts to it – one part is improving the residual control of the winter
weeds, so assessing which herbicide is the best at that, but then also we need to look
at summer weed control as well. So what is the best product for controlling those winter
weeds may not necessarily be the best product for controlling the summer weeds, but maybe
a combination of the two might work.” The fallow trials aim to provide growers in
low rainfall areas with localised data about potential grain yield and quality benefits
- and the associated economic returns - from growing crops to their full potential using
stored soil moisture from winter and summer rainfall.
“We have obviously soil tested the site and then we will follow that through into
next year and the year after and then we will find out exactly what benefit has been delivered
by conserving that water, say nitrogen-wise, compared to where it has been cropped or where
there has been more weeds have been let grow in the fallow. So we want to establish for
people what the net benefit is with nitrogen.” Wyalkatchem grain grower Campbell Jones is
hosting a fallow trial site on his property. He recently started to use a strategic spray
fallow for moisture conservation, weed control and reducing the risks of cropping in increasingly
variable rainfall conditions. He explains the importance of good summer
weed control to the success of the system. “Just noticing from doing the chemical fallow
trials, if you can keep that paddock clean of any weeds at all, your moisture retention
is phenomenal. So keeping the paddocks clean during the summer time is paramount. It is
money in the bank. If you can keep that moisture there, its profit for you at the end of the
year.” Campbell says he hopes the trials will put
some hard data around the amount of moisture that can be saved and used by subsequent crops
in a spray fallow system. “We are hoping that the data they get from
the moisture probe that they have got down there in-crop and also in the chemical fallow
will provide us with definite answers on how much moisture we can save. If that puts it
into a millimetre figure that we can carry over into the following year, it gives us
good confidence whether we put it into wheat, canola or barley that we have a certain amount
of moisture there that we can go ahead with. The chemical fallow will definitely give me
more options. You have cleaned up your paddock and then you have got that stored moisture.
So you have the potential to put a canola crop in because you know you have a fairly
good moisture bank underneath. Likewise, if you don’t get the summer rain, you can safely
go in with a cereal and know you are going to have no dramas whatsoever getting it away.”