Most irrigated crop research programs involve wheat or cotton. This trial is underway to
optimise yields and grower returns from other irrigated grain crops. In its 2nd year the
project, led by FAR Australia with GRDC investment, has another 12 months to run.
The project that we are show casing today is called Optimising Irrigated Grains. Covid
has limited grower numbers attending the trial s field day. What they re looking at is the result
of soil amelioration treatments and agronomic practices. What they want to hear is what
agronomic levers to pull to increase yields, and how soil amelioration interacts with irrigation
to improve water use efficiency. Agronomy and amelioration are the project s main components
and Dr Ehsan Tavakkoli oversees the amelioration research. What we are trying to achieve here is
to improve the size of the bucket in this case and have a better crop access to that subsoil water
after improving the subsoil properties if there is an identified and recognised issue with the soil
either in the subsoil actually or the topsoil. The Optimising Irrigated Grains project has trial
sites across 4 states. The amelioration work is confined to just two locations, in southern NSW.
Noorong which has self-mulching grey soils and Finley with its red soils. At Finley intensive
soil sampling and analysis found no real topsoil issues but several lower down the profile.
We found that there is issues related to subsoil dispersion and slaking and also extremely alkaline
subsoil. Because when you have high pH you have a lot of negative charge on the clay which is
repulsive and so the clay tends to disperse when it comes in touch with water. West of Finley at
the Noorong site both the topsoil and subsoil had issues. There has been a lot of issues in the
surface crusting and a poorly structured topsoil in addition to some issues that we also identified
in the subsoil. So, our soil sampling suggested that the surface application of organic amendments
for example could benefit the topsoil improvements in Noorong site as opposed to the appropriate
level of organic carbon in Finley site and both of those sites receive a surface
application of some of the amendments and also the subsurface application to see
their factorial design and comparison across 4 replicate what sort of crop responses and also
corrections in soil properties we can obtain after a few years of that one-off application. What is
also different about the two sites is their recent cropping history and soil nitrogen levels present
at the start of the trial. The site at Finley in 2018 had a Faba bean crop that failed due
to drought and then the following year the site was fallowed as a lot of redevelopment was done.
So that s led to a very high soil nitrogen level leading into the 2020 crop and that can
have an impact on some of our trials. A one-off application of organic amendment together with
gypsum in year one of the project resulted in 27% improvement in yield productivity of faba bean.
In this case the amendment was pea hay stubble which Dr Tavakkoli said interacted well in an
irrigated farming system. And this has resulted in that significant improvements in yield and
productivity and my hope is and based on our modelling work this suggests that the next 7 to 10
years the residual effect of such a work will last and hopefully will see consistent improvements.
At Noorong oats had been grown before the site was ripped and another plant-based amendment
added. Where we had put out the organic amendment which was lucerne pellets we saw a massive amount
of mineralisation so a release of nitrogen which was very apparent in the subsequent crop of oats
that we put in in 2020. The ripping treatments weren t quite as apparent it was difficult to pick
them over the control in the first half of the season but as the season progressed and moisture
became a little bit tight at the end of winter then where the site had been ripped we actually
started to see some improvements in crop growth but nothing like what we d seen with the extra
nitrogen through the organic amendment. Victoria s Irrigated Cropping Council and NSW based Field
Applied Research Australia co-ordinate research at the project s two main sites Kerang and Finley.
And here as well as at the interstate trial sites agronomy is the project s ongoing focus.
And to evaluate agronomic levers, trial plots are irrigated using either surface or overhead
irrigation. For example it might be that if you sow on one type of irrigation you need a higher
plant population than another type of irrigation or a different variety might require a different
plant population and then you know we ll measure the canopy, how many tillers for example and what
was the dry matter at different stages throughout the crop and how does that affect the yield.
One of the main agronomic levels is Nitrogen rates and the project is aiming to answer the question
how hard can you push nutrition to increase yield? For example in maize we re putting
up to 500 kilos of nitrogen per hectare but we re not finding a response above 250 kilograms
per hectare. In canola we re putting up to 300 kilos per hectare and there s no response above
150 160 and then in durum a similar story, we re going up to 350 kilos of nitrogen per hectare and
our response again is not much above 150 kilos of nitrogen per hectare.
These responses to background soil fertility in combination with fertiliser application
challenge nutrient management thinking. And the results being seen with canola are a good example
of that. The common metric is that you need to get 7 tonne of dry matter at early flowering
and we did achieve that with the highest rate of nitrogen but we also achieve 5 tonne a hectare
at 160 kilos of nitrogen and final grain yield was no different so
we are questing these metrics. Do you need to get your 7 tonne of dry matter at early flowering
when 5 tonne gives the same result. Along with wheat, do you need high rates of seed to get high
tiller numbers when you can get the top yield at lower plant populations. N rates are one part
of a complex business decision for growers. They re also very conscious of water costs and getting
the right balance between optimising yields and cost of production and this is a real challenge.
Do I push for high yield but that s going to take 3 irrigations so water s at this price
so can I afford to do it or is it the best way to do it? Or is it accepting that I m not doing
things agronomically 100% to maximise yield but at the end of the day it will make me more money from
limited water or expensive water that I ve got to use. What will help answer those questions
is a Tasmanian Institute of Agriculture economic project called WaterCan Profit.
It s being run in conjunction with the Optimising Irrigated Grains trials. WaterCan Profit takes
the gross margins from the different crops, the cost of water, other crop input costs,
projected grain yields and returns, to calculate what is the best crop to grow if water is limited
and more expensive. There s a link to the calculator at the end of this video.
The more expensive irrigation water gets the more it s not just simply just grow a crop, water it,
hope that it yields well. We re getting to the stage where it has to yield well,
and it has to yield economically. There were plenty of questions for the project s leaders,
how do you get 7 tonne of faba beans and 5 tonne of canola under irrigation and how was the highest
grade of durum, DR1 with 13 percent protein, achieved? And the answer to all 3 of those
questions seems to come back to soil fertility What we re finding is that we re getting yields
that use up nitrogen much greater than the amount we need to apply to get those yields. So
going forward every year we re going to be taking more off with the crop than what we re applying
and that s an issue that needs to be addressed. Issues and outcomes will shape the last year of
the trial. Most trials will be repeated in 2022 but where a treatment has delivered
no benefit after 2 years it will be stopped and another treatment showing greater promise given
more attention. A good example of that is in maize we did some fungicide work and after two
years we found no result with fungicide. We ve done a little bit of row spacing work in maize
and seen some interesting results, so we are going to ramp that up in the 3rd year. While not every
trial site can hold a field day the agronomic research is replicated at the interstate sites
where similar crop responses are being seen to those here at Finley. We hope that at the end of
the 3 year project that we have developed a suite of what we like to call good management practices
and that those management practices if used will give farmers consistent and reliable yields under
irrigation. Helping to make growers aware of the project s outcomes will be Action Learning Groups
and the research partners involved. And for more information about the WaterCan Profit calculator
and Optimising Irrigated Grains trial reports use the following links.