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nutrient management
FreecalL 1800 677 761
Nicole Baxter
for the grains research and
development corporation
Rural Directions
A trial of South Australian
growers continues to confirm
the financial value of strategic
nitrogen management as
found in Grains Research and
Development Corporationfunded research.
Nitrogen boost: South Australian grain growers
Bruce Nairn (left), Tony Clarke and John Rohde
with CSIRO’s Jeff Baldock and Rural Directions’
Patrick Redden see how well strategic nitrogen
fertilising increased yields.
Strategic nitrogen use lifts
gross margins by $30/ha
At a glance
Growers are encouraged to
trial the financial value of their
nitrogen management strategies.
Trials in South Australia show
the strategic approach of using
minimal ‘up-front’ nitrogen and
adding more at key crop growth
stages can save growers $17–$51
per hectare in fertiliser and
application costs.
But applying nitrogen fertiliser
early in the season still could
be an advantage such as in high
nitrogen demand situations of
wheat-on-wheat paddocks, barley
paddocks following wheat and
to achieve quality specifications
required in oaten hay.
Limiting ‘up-front’ nitrogen fertiliser
applications and only adding more as the
season progresses in response to sufficient
moisture can increase gross margins by
more than $30 a hectare, South Australian
trials show.
According to Rural Directions consultant
Tony Craddock, based at Freeling, SA, the
finding (that has been mirrored in other
trials around the country) is particularly
valuable as growers face an uncertain
climate and rising fertiliser costs.
Savings to be made
Tony and colleague Patrick Redden
quantified the potential savings from
strategic nitrogen application after working
with more than 50 growers.
Their research was part of the Grains
Research and Development Corporation’s
Southern Agribusiness Trial Extension
Network — Nitrogen Project, aimed
at encouraging growers to better match
nitrogen fertiliser inputs to actual
crop demand.
In preparation, growers from the Rural
Directions Cropping Board groups in
Mallala, Owen, Alma, Tarlee and Gomersal
met to discuss previous nitrogen strategies
and their intentions for the 2006 season.
At this meeting, Tony and Patrick
instructed growers how to carry out deep
nitrogen tests and interpret the results.
Value of nitrogen management
To compare the economic value of
strategic versus prescriptive nitrogen
management, each grower selected up to
56 Farming Ahead August 2008 No. 199 www.farmingahead.com.au
two paddocks and tested them for deep soil
nitrogen and moisture during April and
early May.
The project also involved evaluating the
performance of CSIRO’s potential yield and
nitrogen calculator (www.csiro.au/products/
ncalc) developed by CSIRO soil scientist
Jeff Baldock.
By using minimal ‘up-front’
nitrogen, growers can save
$17–$51/ha in fertiliser and
application costs.
Growers were encouraged to trial the
financial value of the two nitrogen
management strategies on two paddocks.
Strategy one (the prescriptive approach)
involved applying most nitrogen ‘up front’
— at, before or immediately after sowing.
Strategy two (the strategic approach)
limited ‘up-front’ nitrogen and added more
at key crop growth stages at rates adjusted
according to seasonal conditions.
Dr Baldock participated in the cropping
board meetings to help growers develop
strategic nitrogen management plans using
his CSIRO calculator.
Mr Craddock encouraged growers to
select uniform paddocks so the nitrogen
strategy was the only variable.
Variety, herbicide and time of sowing
were kept the same.
CROPPING:
nutrient management
How strategies compared
Although only two of the five trials
were harvested due to the dry season, the
two strategies showed observable and
economic differences.
Deep nitrogen testing, coupled with the
use of the CSIRO calculator, indicated no
requirement to apply additional nitrogen in
most focus paddocks given the calculated
low yield potentials associated with the
dry season.
Although some growers were nervous
about avoiding topdressing nitrogen
applications, those who did were financially
in front.
In taking a strategic approach (minimal
‘up-front’ nitrogen) growers saved $17–$51
per hectare in fertiliser and application costs.
Accuracy of yield predictions
Tony said yield predictions of the
CSIRO calculator compared well with
actual yields.
He found most growers were positive
about using the calculator and were happy
with its accuracy although they would
like to see how it performed in a more
‘normal’ year.
The value of deep soil nitrate levels had
become more important in drier seasons.
High fertiliser prices had
prompted growers to
closely evaluate their
fertiliser inputs, making the
deep nitrogen tests a useful
tool to refine nitrogen
fertiliser strategies.
Despite some yield inaccuracy, the
model had been accurate enough to allow
growers to objectively assess their crops’
nitrogen requirements.
In almost all cases, Tony said the model
had advised against adding more nitrogen
as yield potentials had been significantly
lower than average.
Although this had gone against the
instincts of many growers, it proved to be
the correct strategy for 2006.
Do not delay
This said, he cautioned against delaying
nitrogen applications in all situations.
He said there were still instances when
nitrogen fertiliser might be an advantage
when applied early in the season.
These advantages included high nitrogen
demand situations such as wheat on wheat
paddocks, barley paddocks following wheat
How the calculator rates
More than 50 South Australian growers
evaluated the performance of CSIRO’s
potential yield and nitrogen calculator and
identified its best and worst features for
local conditions.
Best features
3Easy to use.
3Increased confidence in not applying
late-season urea in poor seasons.
3Allowed objective decision-making
based on rainfall predictions.
3Helped gain a better picture of
yield potential.
3Useful for in-crop decision-making.
Worst feature
5Too much emphasis on soil sampling on
April 1; not always practical if contractors
are involved.
and to achieve quality specifications required
in oaten hay paddocks.
Contact Tony Craddock
(08) 8525 3000
0417 809 317
[email protected]
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