Wheat
Cropping
Manage nitrogen to avoid haying-off
‘Haying-off’ in wheat crops costs the Australian grain industry up to $200 million each year from reduced yields, higher
screenings and wasted nitrogen fertiliser. This article is based on the research of CSIRO scientist Anthony van
Herwaarden and shows how best to manage wheat to avoid the problems caused by haying-off.
aying-off can occur during a period of
spring drought if a wheat crop has
insufficient stored sugars to transfer to
developing grain.
The resultant grain is small and shrivelled
leading to high screenings and price penalties
at grain receival.
Wheat grown with high nitrogen uses
more soil water and develops a smaller
reserve of stored sugars than the same variety
grown with less nitrogen. High nitrogen
wheat is therefore more likely to hay-off
during a dry spring.
In seasons with good rainfall, the lower
sugar reserve of high nitrogen wheat is not a
problem as the crop is not water stressed and
can fill the grain through photosynthesis
without having to rely on stored sugars to
finish the grain.
But if the season dries out during spring,
the high nitrogen crop becomes more
water stressed than the low nitrogen crop
and photosynthesis (or sugar production)
slows down. With limited stored sugars, the
high nitrogen crop is less able to fill its grain
and crop yield is diminished.
In contrast, the low nitrogen wheat crop,
with higher reserves of stored sugars and
greater remaining reserves of soil moisture,
can continue to fill grain during a drought
period and invariably yields more than a high
nitrogen crop.
Stagger nitrogen inputs
Matching nitrogen supply to the unfolding
season will reduce the chance of haying-off
occurring in a wheat crop.
The aim is to strike a balance between
adding sufficient nitrogen to gain the best
yields and protein but not to over-fertilise and
encourage haying-off.
Haying-off is worse when all the nitrogen is
applied at sowing because the nitrogen
promotes rapid growth and low sugar
reserves. Applying enough nitrogen at the
start of the season to achieve the farm-average
wheat yield allows more nitrogen to be
top-dressed up to the start of grain fill if there
is sufficient rainfall.
Managing the water use of a crop
The proportion of stored soil water and
rainfall used by a crop after flowering has a
large impact on final grain yield and quality.
A crop that uses most of its water supply
before flowering is likely to hay-off while a
crop that has 20 per cent of its water supply
still available for use after flowering will
FA R M I N G A H E A D
No. 141
October 2003
CSIRO Plant Industry
H
Haying-off costs the Australian wheat industry up to $200 million each year. Spring droughts stress the
maturing wheat plants and diminish the amount of sugar available to fill the grain. The problem can be
managed through attention to crop nutrition and disease.
achieve a higher crop yield of better quality.
Plants with access to high levels of nitrogen
at the start of the season will tiller more, grow
faster and use more water by flowering than
crops grown with less nitrogen.
While more tillers equates to a greater
potential yield, lack of water during spring
will cause these plants to hay-off and yield less
than smaller, less-tillered varieties.
Budgeting fertiliser inputs
Getting the nutrition of crops right is
important in making the most of the season.
Budget inputs of fertiliser nitrogen and
phosphorus on crop demand to achieve
average farm or paddock yields, plus some
allowances for nutrients that will become tied
up in the soil.
For example, budgeting nitrogen and
At a glance
• Haying-off in wheat causes yield
losses, small and shrivelled grain
and wastes valuable nitrogen.
• Managing nitrogen input can
reduce the incidence of haying-off.
• Minimising foliar and root diseases
will reduce the impact of spring
drought.
• New wheat varieties are being bred
that are more tolerant of haying-off.
phosphorus for a yield of three tonnes
per hectare is throwing money away if
there are other constraints to production
(that cannot be altered) and which limit a
farm-average yield to 1.5 tonnes per hectare.
On the other hand, there is no point in
fertilising for an average yield of 1.5t/ha if
all it takes to lift the average yield to 2t/ha
is rectifying a trace element deficiency or
rotating crops.
Crop rotation
Rotating crops is the best way to reduce the
risk of soil-borne diseases that limit the yield
of crops.
Collaborative research by CSIRO and State
Departments of Agriculture over the past 12
years has shown that growing wheat after a
brassica break crop increases yield by 20% and
grain protein by 1% compared with wheat
grown after wheat.
Root disease will diminish the ability of
the crop’s root system to extract water and
may also reduce the store of soluble sugars
as they are redirected to the roots to fight
the infection.
Crop rotation will minimise disease
risk and result in more efficient use of
costly inputs.
Leaf disease
Leaf diseases reduce the photosynthetic
area of the crop, resulting in less sugar
production for plant growth and grain fill.
Some leaf diseases also stimulate the
production of an enzyme, ‘invertase’, in
the leaves of the crop. Invertase prevents
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Wheat
the transport of sugar from the leaf,
preventing it from reaching the grain and
can have a negative effect on crop yield, and
result in high screenings, even if water supply
is adequate.
Leaf diseases are best managed by growing
resistant varieties, achieving effective weed
control and managing stubble and rotations
appropriately.
Sowing time
Sowing as close as possible to the break of
season while taking into account any frost
risk at flowering, is one of the simplest and
most effective ways of maximising crop
production and minimising yield losses
caused by haying-off.
The earlier a crop flowers, the more likely it
is that the plants will have sufficient access to
soil water reserves, receive further rainfall
and experience cooler temperatures during
grain filling.
On average, there is a yield penalty for each
day that sowing is delayed after the frost risk
is reduced.
Breeding for reduced haying-off
Since stored sugars decrease haying-off in
wheat, breeding varieties that actively
accumulate stored sugars and that do not
use up these stored sugars to increase
tiller numbers should reduce the incidence of
FIGURE 1 Soluble sugar trade-off
Water soluble carbohydrates
at flowering (%)
Cropping
35
30
25
20
15
10
5
0
0
5
10
15
Protein at flowering (%)
In the event of a spring drought, high nitrogen
wheat does not have the sugar stores to fill
developing grain and haying-off occurs.
Source: CSIRO Plant Industry.
haying-off in wheat crops.
CSIRO researchers have evaluated a
range of ‘reduced tillering’ wheats over
the past few seasons to determine their yield
potential under different environmental
conditions.
They have discovered that low tillering
wheat lines produce sufficient tillers to
satisfy yield potential in a given area
but, interestingly, do not produce a profusion
of tillers in response to soil or bag nitrogen.
This means they do not ‘waste’ soluble sugars
on excessive tillering but still have some
stored sugar reserves available to fill grain
during spring.
The researchers found the best of the
reduced tillering lines accumulated 20%
more stem sugars by flowering and
out-yielded locally adapted varieties by 10%.
The reduced tillering lines also produced
kernels that were 25% larger, reducing the
incidence of high screenings.
Genotypes with the ability to accumulate
high stem sugars are currently being used
in a CSIRO wheat breeding programme
to increase grain yield under water-limiting
conditions.
The CSIRO researchers are confident the
reduced-tillering varieties will be available to
farmers in the future. They believe these
varieties will be better suited to the
production of Australian hard and prime-hard
grades of wheat.
The reduced tillering varieties will also be
more tolerant of the seasonal conditions
that trigger haying-off and will be less
prone to high screenings because of their
larger kernel size.
For more information contact Anthony
van Herwaarden, CSIRO, by email on
[email protected],
phone (07) 3214 2320 or fax
(07) 3214 2920.
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FA R M I N G A H E A D
No. 141
October 2003