Pacific Seeds Hybrid Corn Agronomy guide 2008 ... - Directrouter.com

Pacific Seeds
Hybrid Corn
Agronomy Guide
2008/09
CONTENTS
The Australian corn crop................................................................................2
About the corn plant and climate .................................................................2
Corn agronomy.................................................................................................4
Choosing the right type of corn................................................................. 11
Planting the crop............................................................................................ 14
Diseases of a developing and mature corn plant.................................... 16
Harvesting and storage................................................................................. 17
Other uses of corn........................................................................................ 18
Corn for silage................................................................................................ 18
Tips for making better quality silage.......................................................... 20

The Australian
corn crop
In Australia corn is, comparatively speaking, a minor summer
crop with an annual production of 350,000t – 450,000t,
most of which is consumed domestically. Corn produced in
Australia is approximately 50% rain grown or dryland and 50%
grown with the assistance of irrigation. All Australian corn is
non GMO.
The peak body representing Australian corn growers and the
industry at large is the Maize Association of Australia, with
Tony Cogswell at the helm as President. For more details on
the association go to www.maizeaustralia.com.au.
Corn grain varies greatly from very soft (starchy) to very hard
(hard endosperm), which determines end use. Before we
segment the industry into grain types we should understand
the different corn grain types.
Scale of hardness
SOFT/FLOURY STARCHY SEMI-DENT SEMI-FLINT HARD/FLINT
DK 477 Hycorn 901 XL 80 Burst
Hycorn 504 Hycorn 345
Hycorn 502IT
Hycorn 345IT
Hycorn 533
PAC M727
Hycorn 424
PAC M712
Hycorn 675IT
A typical analysis of flint and dent types on a
dry basis is:
FLINT
Grown under the same conditions you would expect
the highest protein to be in quick flint, followed by
med-slow flint, quick dent and the lowest in med-slow
dent.
There can be two types of starch contained
in corn:
Regular yellow corn and white corn contains
approximately 73% amylopectin and 27% amylose.
4 Waxy corn produces 100% amylopectin.
DENT
Starch content (%) 66.5 72.0
Protein content (%) 13.5 10.0
Oil content (%) 6.0 5.0
Fibre content (%) 14.0 13.0
4 Hi-amylose can be up to 80-90% amylose and
10-20% amylopectin.
4 14% moisture content is the industry delivery
standard and a safe storage level.
About the corn plant
and environment
Although corn is a summer crop it is not a heat loving
plant like cotton (an arid plant). Corn is a sub-tropical
plant rather than a temperate plant and therefore
prefers milder conditions with plenty of sunshine
without excessive heat. As well as being temperature
sensitive, the corn plant is also sensitive to day length.
Corn is a ‘short day’ plant as the day length
(photoperiod) affects the time from germination to
initiation of floral parts.
Critical day length appears to be between
14.5 and 15 hours. This means corn grown
between latitudes 23° north and 23° south do not
experience long days. Considerable genetic variation
for photoperiod sensitivity exists in corn germplasm.
There is also an interaction between day length
and temperature which also has considerable
genetic variability.
As a result of these characteristics of the corn plant
the same hybrid planted in the south compared to
the tropical north will take longer to flower, will have
more leaves and will be taller.
2
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

Stage
Emergence
VE V2 V5 V8 V12 V16 R1 PM HARVEST
2 leaves
fully
emerged
5 leaves
fully
emerged
Tassel & ear
initiation
8 leaves
fully
emerged
12 leaves 16 leaves Pollination
20 leaves
Planting
Days -7 0 7 21 35 46 56 63 105 130
Growth
Stages
1 2 3 4 5 6
Adapted from Date, A.B. Shaw, A.J., and Sykes, J.K. (1990), Weed control in summer crops 1990, NSW Agriculture & Fisheries
The stages of grain fill in corn
Pollination
Cell division
Starch deposition
65 days
Protein deposition
Drydown
1. Pollination
Stress will reduce the number of grains set but not
grain quality.
2. Cell division
Stress will prevent proper cell division and
can reduce grain size but not protein/starch
components. Bushel weight can be affected in
some genotypes.
3. Starch deposition
Stress will reduce starch deposition and change
protein/starch ratio and seriously affect density
and milling qualities.
4. Protein deposition
Stress at this stage has the greatest effect on grain
density and millability. The storage proteins are
laid down late in grain fill and act as a super glue to
bind the starch granules into a very dense matrix.
The role of nitrogen is critical in late grain fill to
make or break ‘grits’ corn, of the right genotype.
Low N = Low protein (< 8.5 %) = Starch type
High N = High protein (8.5 – 10 %) = Grit type
Sunlight provides the energy needed to produce
starch. Southern Australia’s long sunny days of
moderate temperatures are ideal and permit tall, leafy
and high yielding plants. In association with a good
soil structure, which allows rapid early root growth,
a deep and dense root system will help ensure high
yields. Unfortunately root growth will be restricted in
areas with dense subsoils, hard setting topsoils, high
water tables or salinity.
In Northern New South Wales and Queensland higher
rainfall is normally accompanied by increased cloud
cover, shorter days and high average temperatures.
Although most of these inland areas do have soils that
are more fertile, with better water holding capacity
than southern soils.
The best corn hybrids have a genetic yield potential
of around 36t/ha of grain. This potential depends
on individual cases according to climate, time of
planting, plant populations, soil types and pH, water
management, nutrition, weed control, presence of
disease and other environmental factors.
The yield potential in Australia is approximately
20 - 22t/ha because of the harsher climate. We
only have to look at seasons 2002/03, 2003/04 and
2005/06 to realize how harsh the conditions can be.
Excessive daytime temperatures of 40°C+ coupled
with night time temperatures of 28° – 30°C, for
periods of up to 10 days, during the crucial
pollination/seed set period dramatically reduced
yields. With this excessive heat it also stretched
resources trying to keep moisture up to these crops
at such a critical time.
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 3

Corn Agronomy
Soil types
Ideal soil types for corn production are naturally
fertile deep sandy loam to clay soils with good
water holding capacity and, at the same time, well
drained with a neutral to slightly acid pH (6.5 – 6.7).
Corn is also much more susceptible to saline soils
when compared to other crops like sorghum, wheat
and barley. Some people believe the soil is only
a means of supporting the plant and we just add
fertiliser and water.
Australian corn breeders have served us well with
a lot of the trialing work carried out on the higher
pH alkaline soils. Generally, the pH levels inland on
the clay based soils are much higher than what is
experienced on the coast or Victoria.
Experts will tell you that corn does best on neutral
to slightly acid or alkaline soils. But a lot of the inland
areas where large areas of corn are grown, it is not
uncommon to have a soil pH of up to 7.5 or even 8.0.
Not only is there a range in climatic conditions in
Australia but also a very broad range of ancient soil
types which are, in most cases, low in organic matter.
Once again the potential yield is lowered in most
cases because the soil type is not ideal.
A lot of inland corn is grown on clay based
soil which, in general terms, is good soil with good
water holding capacity but is certainly more prone to
water logging with either excessive summer storms
or over irrigation early in the plant life. This same soil
type is also more prone to compaction because of its
fine particle size and clay content.
The corn plant is more vulnerable to soil compaction
and it is having a detrimental effect on corn yield in
some irrigation systems, particularly if farmers are
forced to harvest under wet field conditions or field
preparation occurs after a wet winter. In a lot of cases
the compaction is occurring in the bottom of the
actual furrow from land preparation through to post
planting operations.
Soil compaction has multiple effects on the plant:
4 Reduces water holding capacity and therefore
increases water logging (causing an anaerobic
environment)
4 Reduces the plants ability to develop an efficient
root system to scavenge both moisture and
nutrients from depth
4 Water scheduling will be shortened because of the
plants inability to scavenge at depth even though
the probe may indicate otherwise
4 Makes the plant more prone to root, stalk and
grain diseases because it is being put under stress
through its inability to scavenge.
Seedbed preparation
With the uptake of zero tillage, tram lining and
permanent beds (or bed renovation) there has been
a reduction in the effect of compaction, particularly
under dryland farming operations.
If compaction is a known problem then deep
ripping or sub soiling is suggested. Also ripping the
furrows will enhance water infiltration with bed
or furrow irrigation.
Both soil structure and moisture conservation
have also improved using minimum tillage/zero
tillage techniques.
As has already been established, corn like most crops
is prone to water logging, therefore irrigation fields
that have not been properly levelled will suffer with
unevenness across the field and a reduction in yield.
If conventional farming practices are being used then
a good fine seed bed is desirable. Also if you are
planting dry and watering up, there is no need to plant
deeper than 2-4cm.
Corn has a large seed which allows growers the
flexibility to plant a little deeper if chasing moisture,
so long as the ground temperatures are adequate.
Nutritional requirements
As corn is a big producer of dry matter, it is also a big
user of nutrients which a lot of the Australian soils
are not capable of supplying without the addition of
fertilisers. The first advice is to regularly have soils
tested so you are aware of the nutrient status, both
macro and micro, pH and organic matter.
4
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

Once you have analysed soil test results you can plan
a fertiliser program based on available nutrients and
most importantly your budget or expected yield.
Remember if growing corn for silage you will need
a slightly different fertiliser program than what you
would for grain.
The big three primary nutrients required for a corn
crop are Nitrogen (N), Phosphorus (P) and Potassium
(K) which represent 83% of total nutrients.
The secondary nutrients Sulphur (S), Calcium (C)
and Magnesium (Mg) take another 16% which means
the micronutrients only represent 1% of the total
nutrient uptake.
Corn takes the large majority of its potassium
by silking but requires a supply of nitrogen and
phosphorus beyond grain fill. The accumulation of
water, nitrogen, phosphorus and potassium is rapid
in the early stages of growth beyond the four to five
week period.
Fertiliser application and timing is extremely
important with corn being an aggressive user of
nutrients, particularly in the period leading up to
tasselling. So it is very important that the nutrients be
available to the plant when it is most needed.
Because of the high levels of nitrogen required
nitrogen fertiliser is normally applied preplant in
the form of urea or anhydrous ammonia or at
planting if applying between the rows. Most corn
growers spit apply their nitrogen with approximately
60-70% applied preplant and the remaining applied
either water run or side dressed prior to tasselling.
WEEKLY REQUIREMENTS
(as percentage of total need)
MATURITY
% N % P % K % Water
17 weeks
less
than 1
less
than 1
–K
less
than 1
16 weeks
less
than 1
1
–K
1
15 weeks
less
than 1
2
–K
2
14 weeks
less
than 1
5
–K
3
13 weeks
2
8
–
5
12 weeks
4
19
–
6
11 weeks
6
11
1
8
10 weeks
10
13
5
11
SILKING
12
15
8
12
TASSELING
16 11 16
12
7 weeks
15
10
20
11
6 weeks
14
7
21
10
5 weeks
11
4
16
7
4 weeks
7
2
9
5
3 weeks
2
1
3
4
2 weeks
less
than 1
less
than 1
1
2
1 week
less
than 1
less
than 1
less
than 1
1
EMERGENCE
less
than 1
less
than 1
less
than 1
less
than 1
Incitec information bulletin dryland maize
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 5

Nutrient uptake by corn (Assuming 10% protein)
kg/ha
N P K S Mg
Grain 2.5t/ha Grain 40 9 11 4 6
Silage 22t/ha Stover 28 4 54 6 11
7t/ha DM TOTAL 68 13 65 10 27
Grain 5.0t/ha Grain 80 17 22 8 10
Silage 37t/ha Stover 56 9 90 10 19
11.8t/ha DM TOTAL 136 26 112 18 29
Grain 7.5t/ha Grain 120 25 32 12 14
Silage 52t/ha Stover 84 11 125 14 26
16.6t/ha DM TOTAL 204 36 157 26 40
Grain 10t/ha Grain 160 32 41 15 17
Silage 65t/ha Stover 112 14 166 17 35
20.8t/ha DM TOTAL 272 46 207 32 52
Grain 12.5t/ha Grain 200 39 51 18 20
Silage 75t/ha Stover 140 16 194 20 38
24t/ha DM TOTAL 340 55 245 38 58
Grain 15.0t/ha Grain 240 46 60 21 21
Silage 86t/ha Stover 168 19 224 22 43
27.5t/ha DM TOTAL 408 65 284 43 64
These figures should be used as a guide only as the amount of fertiliser applied will depend on the soil type,
especially clay percentage.
Usually the other nutrients are applied pre-planting or
at planting in the form of starter fertiliser.
Placement of fertiliser is also important as the
emerging corn seedling can only tolerate small
amounts of N (5kg/ha) and P (10kg/ha) in direct
contact with the seed. At the same time it is
important that the emerging seedling has access to
pop-up fertiliser, to give it a good start.
Under cool, wet conditions in soils that are high in
pH, uptake of some nutrients can be inhibited and
may require foliar sprays to correct the in-balance.
The main nutrients affected are zinc, boron, iron,
manganese and copper.
Nitrogen
Nitrogen is by far the most important nutrient for
producing high yielding crops but the need to try and
balance the whole equation should not be forgotten. If
a soil is deficient in even a minor nutrient, high levels
of nitrogen are not going to overcome this deficiency.
Because nitrogen is the most important nutrient
its management is crucial. Not only is there a need
to apply enough to feed the crop but it needs to
be available at these crucial growth stages. Applied
nitrogen can be lost before the plant has the chance
to use it by leaching, denitrification (water logging
or an anaerobic environment) and immobilisation by
micro organisms. Nitrogen is an essential component
of organic compounds, protein, nucleic acids and
chlorophyll. Remember if removing the whole crop
for silage you will require approximately 75% more
nitrogen than for grain production.
The results of nitrogen deficiency in a corn crop
Phosphorus
Phosphorus is an essential element in the
development and growth of the corn plant. It aids in
the production of nucleic acids for reproduction and
6
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

grain production, lodging resistance, root growth and
crop maturity. Phosphorus is also important in the
transfer of energy within the plant.
Phosphorus is fairly immobile in the soil so it is
important to place it close by the plant line (5cm to
the side and 5cm below the seed) so that the young
plant roots have ready access. Under cool and wet
conditions early in the season, coupled with high pH
soils, young corn plants often have trouble accessing
enough phosphorus until conditions improve.
Potassium
Potassium is important in the corn plant for the
circulation of sugars, starch formation, nitrogen
uptake, photosynthesis, enzyme activation, lodging
resistance, disease resistance and grain fill.
Potassium can be a complicated element in the fact
that soil tests may show good reserves of potassium
but not always in a form accessible to the plant. Like
phosphorus, potassium is usually applied preplant or
at planting in an easily accessible band, as potassium is
the element that is taken up the quickest by a growing
corn plant (80% by tasselling).
Potassium is often overlooked by silage growers, and
hay producers, with a lot of potassium contained in
the stover of the plant. Remember a 10t/ha corn grain
crop uses approximately 39kg of potassium but the
same crop, if taken off for silage, will deplete the soil
of 183kg of potassium.
Sulphur
Sulphur is a constituent of amino acids, vitamins and
enzymes. Traditionally most of the Australian soils
have acceptable levels of sulphur but lower levels are
appearing on the heavy black soils of northern New
South Wales and the Darling Downs where there has
been a long cropping history. Responses appear in low
organic situations and cool and wet conditions early in
the plant’s life.
Zinc
Zinc is a growth regulator. Corn is particularly
sensitive to soil zinc deficiencies, particularly on heavy
clay soils with a high pH and cool conditions early in
the plant life. Cut or fill areas will often be deficient
in zinc for a few years. Most of the zinc is taken up
in the first four weeks of the plant’s life, therefore
it is essential it is available from day one. Once zinc
deficiency symptoms are evident, yield losses are
already being experienced.
Corn growers on susceptible soils should implement
a long term program to overcome zinc deficiencies
using zinc oxide or zinc sulphate monohydrate well
in advance. Zinc can be applied by water injection
using zinc sulphate heptahydrate, meaning it is
Severe zinc deficiency results in stunted plants
readily available. Often foliar applications are applied
when symptoms are evident and may require two
applications to get a severely affected crop to recover.
These days fertiliser companies also have zinc in
some starter fertiliser blends which lends itself to an
ongoing program.
Molybdenum
The main use for molybdenum in a corn plant
is in the enzyme system for nitrate reduction.
Molybdenum deficiency is not usually a problem
but some coastal acid soils can be deficient and the
situation is easily corrected with the addition of
molybdenised superphosphate.
Animal manure
Manure can be a valuable source of nutrients and adds
organic matter to the soil thereby helping the water
holding capacity. Not only does it contain the main
nutrients N,P,K but it also is a good source for micro
nutrients. In fact soils that have manure regularly
applied seldom have micro nutrient deficiencies.
Nitrogen is lost to the air as ammonia (NH3)
whenever fermented manure lies on the soil surface
and dries out. The longer it has been stored before
spreading, the greater the loss. Manure that has been
stored should be worked into the soil as soon as it is
spread. Not all the nutrients are available to the plant
in the first year but as a guide a tonne of dry manure
could contain up to 2.3% N, 1.4% P and 2.8% K.
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 7

An analysis will give an idea of the nutrient value
of the manure. Application rates of 10t/ha applied
are not uncommon, particularly with contract silage
growers who have ready access to manure from
neighbouring feedlots.
Corn water usage and management
Corn is one of the highest yielding crops for both dry
matter and grain production per hectare. As a result
it has a high water requirement. It also is one of the
most water efficient crops because it produces a
large amount of grain and dry matter per millimetre
of water. But it must have adequate water available
to fully achieve this potential. At the same time we
should not underestimate the yield losses that can
occur from too much water or water logging.
Most damage occurs in very young crops when they
are trying to develop their massive root system. As
previously mentioned water logging is a result of badly
drained soils or fields that are poorly developed,
excessive rainfall or irrigation. Therefore too much
water in the root zone can be as detrimental as not
enough water being available to the plant.
Yield reductions of up to 50% can result if corn is
wilted for four days at the end of the pollination
period. Even in the dough stage four consecutive days
of wilting can reduce yield by 40%. On the other end
of the scale four days of wilting at least a week prior
to tasselling only had a 10% reduction in yield.
Corn is moisture stressed when the edge of the
leaf starts to curl inwards. Under hot, low humidity
conditions, stress symptoms may occur despite
adquate soil moisture and before the refill point has
been reached.
Just like nitrogen and phosphorus the corn plant uses
the majority (70%) of its moisture requirement three
weeks either side of tasselling.
Corn has a much longer grain filling period than crops
like sorghum, roughly one third longer, hence the
importance of water management during this period.
A high yielding corn crop will use between 600mm
and 850mm of water depending on location and
seasonal conditions (temperature, rainfall, wind,
humidity). Long seasons and cloud free days
contribute to higher water use.
Daily water use varies during the season depending
on growth stage and weather conditions. The
crop’s ability to take up water increases as the
canopy develops, peaking at the silking stage.
Weather conditions which are hot, dry and sunny
will increase the crop’s water requirement. Taller
and denser crops will use more water than shorter
crops because they intercept more sunlight and are
more exposed to wind. It is important to have a
knowledge of soil water depletion and the ability
of your soil to hold water.
The effects of moisture stress on corn at different stages
Early growth stage Affects leaf cell enlargement resulting in smaller leaves, a shorter canopy and a
reduction in potential yield.
Pollen shed
Silking/fertilisation
Grain fill
Pre-physiological
Severe moisture stress at pollination will give poor pollination and reduced kernel
development. Yield losses at this stage can be as high as 5% per day.
During this three week period maximum water usage occurs and a stress during the
early part of this period will affect kernel numbers while stress during the latter part
will affect kernel weight.
Stress at this point will hasten maturity, reducing photosynthesis and starch
production. After a period of severe water stress, the corn plant may take several
days to recover despite plentiful soil moisture.
The last watering is important for final kernel size and therefore weight, maturity
especially for producers growing contracted grit corn.
Inches
0.4
DAILY WATER USE BY CORN
CRITICAL
STAGE
% Yield
Reduction
0
CORN YIELD REDUCTION
DUE TO MOISTURE STRESS
10
0.3
20
0.2
30
40
0.1
50
60
0
EMERGENCE
FULL
TASSEL
POLLI-
NATION
SOFT
DOUGH
MATURE
100
EMERGENCE
FULL
TASSEL
POLLI-
NATION
SOFT
DOUGH
MATURE
Iowa State Univ.
8
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn
Moisture Management Dekalb Research Notes No. 14

A corn crop will only extract a portion of available
water before moisture stress sets in. Often the soil
profile may not be fully wet due to insufficient water
applied, restricted infiltration or excessive runoff.
It is important to base irrigation periods or
‘scheduling’ on the allowable depletion or allowable
water deficit at various stages of the season. This is
often called the refill point. Allowable depletion is
the point below which the crop may experience yield
losses due to moisture stress.
As roots are not fully developed prior to tasselling
it is suggested that depletion does not exceed
40%. During tasselling and grain fill this figure can
rise to 50% unless extreme temperatures prevail.
Depletion at maturity can be up to 75% under
moderate conditions.
A rough guide is that an irrigated corn crop in
Southern New South Wales/Victoria will receive
10 -12 waterings during its life (longer days, fewer
cloudy days and water holding capacity is lower
than in Northern New South Wales). During peak
water use, watering may take place every 7-10 days,
depending on temperatures. On the other hand
in Northern New South Wales/Queensland 5 - 7
waterings are usually required with scheduling every
10 - 14 days, again depending on temperatures.
Weed control in corn
Summer weeds and grasses are very aggressive
and compete with young corn plants for moisture,
nutrition and light. Therefore early weed control is
essential in corn crops before the canopy shades the
soil surface.
Nutgrass infestation in corn
Traditional cultivation will certainly help reduce
weed competition very early on, but not post
planting. Inter row cultivation on its own or
coinciding with side dressing is another method
of mechanical weed control. In more recent times
shielded spraying has proved popular using a
knockdown herbicide like Roundup ® .
By far the most efficient and effective form of
weed control is by the use of herbicides. There
are a very good range of herbicides registered for
weed control in corn ranging from pre emergent
through to post emergent.
HErbiCidE APPliCATiON - mAizE (Source: NSW Agriculture)
Stage VE
Emergence
V2
2 leaves
fully
emerged
V5 V8 V12 V16 R1 R5
5 leaves
fully
emerged
Tassel & ear
initiation
8 leaves
fully
emerged
12 leaves 16 leaves Pollination
20 leaves
Dent
Planting
Height (cm) 0 10 30 60 270 270
days -6 -2 0 7 18 28 42 56 65 100
Pre-emergent application
Pre-plant application
Avoid Spraying
Post-emergent application
Atrazine
2-3 leaves Dicamba
10-90cm or 42 days
2,4-D amine
10-20cm 20cm - before tasseling: drop nozzlies only
Starane ® 200
3-5 leaves 6 leaves to tasseling: use droppers
Tordon ® 75D
4-6 leaves: using drop nozzles if mixing with 2,4D
MCPA
25-60cm: drop nozzles only
Avoid Spraying
Harvest aid
2,4-D amine
from dough stage
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 9

Always read the application directions on the label.
Some residual herbicides have plant back restrictions
for following crops, so careful planning of a herbicide
program is required to ensure cropping options are
not unduly restricted. Consequently it is important
that there is an understanding of the herbicide history
of the particular paddocks as there may have been a
residual herbicide applied on a previous crop to which
corn is sensitive.
Some of the registered herbicides used in corn either
on their own or in combination include Atrazine ® ,
DualGold ® , Primextra ® , Eptam ® , Stomp ®
and the hormone chemicals (post emergent) Starane ® ,
2,4-D Amine ® , Dicamba ® , Tordon 50 D ® and MCPA ® .
Of the hormone chemicals, Starane ® is the softest
on corn and attention should be given when applying
these herbicides to ensure they are applied at the
correct stage and the crop is not under stress. It is
recommended to use droppers between the rows
to avoid applying chemical to the whorl. Otherwise
damage to the reproductive parts of the plant and
lodging can result. For more detailed information on
herbicides and their application please contact your
local agronomist, reseller or chemical representative.
Farm hygiene should also be maintained around fence
lines, storage dams, waterways and channels so as to
keep in check the weed seed bank. Finally clean crops
and surrounding areas will help reduce the build up of
insects and some diseases.
I.T. technology
The I.T. trait incorporated in some of the Pacific
Seeds’ hybrid corn range stands for ‘Imidazolinone
Tolerance’. Imidazolinone (IMI) is a family of
herbicides that has the potential to control many
important weed species that cause yield and quality
reduction in many corn growing regions of Australia.
The I.T. or Clearfield ® trait for corn is a Non-GMO
herbicide tolerant cropping system. I.T. herbicide
resistance was developed using traditional plant
breeding techniques in 1988. This research isolated
a naturally-occurring I.T. gene that is dominant
in nature. This essentially means that an I.T. corn
parent line can be crossed to a non-I.T. parent line,
to produce hybrid seed that has complete tolerance
through its dominant nature. This has many benefits
over some of the competitor products that require
copies of a recessive gene in both parent lines to give
adequate tolerance.
Corn hybrids with the I.T. trait have shown not to
cause any significant yield penalty over conventional
hybrids. In most cases performance is equal to or
slightly higher in I.T. varieties. This is an important
point to consider with I.T. hybrids – no other hybrid
attributes, either agronomic or performance, are
compromised when the trait is incorporated into
a variety.
In Australia, the herbicide registered for use on
I.T. varieties is Lightning ® . This is a broad-spectrum
herbicide for knockdown and residual weed
control in I.T. varieties. A post-emergence
application of Lightning ® herbicide controls over
50 broadleaf and grass weeds by both contact
and residual soil activity for the later germinating
weeds. Lightning ® will suppress and control many
hard-to-kill grass weeds including Johnson Grass,
Barnyard Grass and Nutgrass.
Due to the residual effect of Lighting ® , careful
consideration should be given to plant back intervals
for crops that follow on. Plant back periods
vary depending on the crop to be planted and
environmental conditions. Refer to product label for
more comprehensive details.
Soil insects affecting
emerging corn crops
Emerging corn crops are prone to attacks from soil
insects and if left unchecked a costly replant may
be the only option, with no guarantee the same will
not happen again. Seedling mortality of 30-40% will
have a marked affect on yield due to the lower plant
population. Soil insects are more prevalent in early
spring, coinciding with rising soil temperatures and
pupae/ larvae moving from deeper in the soil.
10
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

Changing farming practices, such as reduced tillage,
zero tillage and permanent beds, may actually favour
the build-up of some soil insects. More traditional
forms of cultivation plus deep ripping seem to have
an adverse affect on pupae/ larvae and therefore soil
insect populations.
Great progress has been made in the last few years
with the release of insecticides for the control of soil
insects. The older style insecticides that are either
applied in a granular form with seed like Counter ®
or sprayed in furrow like Lorsban ® are still popular.
Semevin ® was one of the first insecticides to be
applied to the seed prior to planting but the newer
releases such as Gaucho ® , Cosmos ® and Cruiser ®
have proven more popular and are more user friendly
for the operator as they do not have to directly
handle the chemical.
Pacific Seeds Elite ® treated seed has Gaucho ® applied
to the highest quality seed. The main soil insects
controlled are wireworms, false wireworms, black
field earwigs and African black beetle.
Still popular in Queensland, where it is registered, is
the use of beetle bait which is applied to the surface
of the soil for the control of above ground insects
such as African black beetles, false wireworms, field
crickets, wingless cockroaches and black field earwigs.
From time to time grasshoppers, field crickets and
wingless cockroaches can build up in numbers to
become a problem. Control with a surface spray of a
registered insecticide may be warranted.
Insect pests of a developing corn crop
There are several pests that attack corn plants during
the vegetative, reproduction and grain fill stages
but the most significant are the corn earworm or
heliothis larvae and in some areas the two-spotted
spider mite. Others that can cause yield loss are the
corn aphid, monolepta beetle, green vegetable bug,
locusts and maize weevil.
In seasons where heliothis have over wintered and
numbers are high early in the season, and there is
an early egg lay evident by the perforated unfolding
new leaves. Hatching larvae will forage on tassels
and silks and if infestation is severe, can cut the silks
off reducing seed set. Once the larvae grow it is
uncommon to have more than one in each cob tip.
They often do not do a lot of damage at this stage,
unless the numbers are severe and then they may
start borrowing into the side of the cob. If this is the
case these cobs are predisposed to cob rots.
If the signs of a large egg lay appear then spray prior
to canopy closure. If you leave it until silking or later
it will be hard to get chemical penetration into the
canopy. Remember it is too late if you see large larvae
(30-50 mm) in the crop as it will be nearly impossible
to control.
With the incidence of hot and dry summers,
particularly over the last few years, infestations of
the two-spotted spider mite have been experienced.
Most of these infestations have occurred in the
M.I.A. and Liverpool Plains with the highest pressure
occuring during and after grain fill. The mites first
start on the lower leaves and work their way to the
top leaves causing premature senescence of the leaves
and in severe cases yield loss, grain size reduction
and lodging. Visual symptoms of a mite infestation
are webbing on the under side of the leaves and the
leaves are a washed color.
Choosing the right
type of corn
Once the decision has been made to include corn
in a summer cropping program, thought then must
be given to which market you are aiming at and the
group of varieties or variety that best suits your
situation. All the different marketing options have
been previously discussed so we can assume you have
identified your target market.
Maturity
In the USA corn belt maturity is very important
because of the relatively short growing season, a delay
in planting of three or four days may mean changing
to a different hybrid that has a slightly shorter CRM.
In Australia because of the latitude, except for the
southern areas, there is a wide planting window and
maturity is not as critical.
Longer season varieties (111 - 130 CRM) grown from
the Liverpool Plains north have a higher yield potential
than the quicker maturing varieties, but further south
the quicker varieties (108 – 111 CRM) have similar
yield potential. Yields in the 100 – 111 CRM maturity
have improved over the last 10 years as this is the
dominant maturity group in the USA corn belt.
Quicker maturity varieties are planted outside the
chart below due to:
4 water cutbacks or wanting to finish the crop
before the peak water requirements for other
crops in the hot January-February period
4 delayed spring planting with the aim of beating the
summer heat before tasselling
4 a late plant may be considered and there is a
threat of an early frost interfering
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 11

Adaptability
A variety does not perform the same under all
conditions. The best varieties should yield and
stand relatively well in both favourable and
unfavourable conditions. When choosing varieties
they should perform consistently under the chosen
growing conditions.
Disease resistance
A description of diseases which affect corn grown in
Australia is found on page 16 of this agronomy guide.
The diseases can be split into cob rots, stalk and root
rots, viruses, smuts, leaf blights and leaf rusts.
The incidence and severity of disease outbreaks
is dependant on a number of factors including
management (water, nutrition and crop hygiene)
location, planting date, seasonal extremes, infestation
by insects, cultural practices, populations and husk
cover giving cob protection.
Most of the hybrids released in Australia have an
acceptable level of disease resistance.
Other considerations
Suckers or tillering is not only undesirable but
also looks extremely untidy. Plant breeders try to
eliminate this trait in their breeding programs even
though it is very seasonal.
Some varieties are more prone to tillering than
others. Tillering is usually triggered by high levels of
nutrition, especially nitrogen availability to the plant
early in its life, adequate moisture availability, cooler
temperatures early in the crop’s growth and lower
plant populations.
Sometimes these tillers may have hermaphrodite ears
on top of the tiller but usually by harvest time the
birds have raided the grain that has set. Research has
shown there is no yield penalty with tillers. Farmers
often believe the plant uses moisture and nutrients to
grow tillers and in some cases a bit of grain on top.
Later in the season the main plant actually draws back
the nutrients as the tillers tend to die off.
Some hybrids, particularly three way crosses,
in very good conditions can produce multiple cobs but
they are usually expressed at lower plant populations.
Year in, year out, a variety with one good cob that
flexes its length rather than the number of cobs is
more desirable.
Husk cover is an important consideration for coastal
environments where protection from the weather is
crucial. Open husk varieties grown on the coast tend
to have more cob rots than tighter husk varieties.
Tighter husk cover on processing hybrids is also more
desirable reducing infield stress fracturing.
On the other hand a loose husk cover is often
considered an advantage for inland growers as it
encourages rapid dry down. Recent findings have
found a higher level of mycotoxins in loose husk
cover varieties compared to tighter husk cover
varieties.
Varieties with a longer shank, which allow cobs to
hang over approaching maturity, have less
cob damage than varieties with upright cobs
at maturity.
The final decision – which variety
Like a lot of crops it is advisable to spread your risks
by planting a number of varieties if the end market
allows you, even varying the maturity.
Once again it is important to take into consideration
that the best yielding variety from last season is not
necessarily the best selection. Thought needs to be
given to varieties that have performed over a number
of years in good and bad seasons. Always look for trial
data in your local area if not from your own property
or ask your neighbour.
Other sources of trial data may be accumulated by
government extension officers like the Department of
Primary Industries and Fisheries, private consultants
and seed distributors. For new corn growers it is
worth considering completing your own on-farm
evaluation trial with a few comparable varieties to the
one you have chosen.
A guide to the general maturity plantings in Australia
LOCATION
C.R.M. MATURITY
Tasmania, Gippsland and Western Districts
Under 100 CRM
NE VIC, SA and southern tip of WA
97 – 113 CRM (can be slightly longer for silage)
MIA, Lachlan and Macquarie Valleys
105 – 118 CRM
(longer end of range for grits & silage)
Liverpool Plains and Northern NSW
108 – 118 CRM
Sydney basin, mid/north coast,
115 – 126 CRM
Northern Rivers, NSW.
Darling Downs and Burnett
108 – 120 CRM
Central Queensland and Callide Dawson
111 – 118 CRM
North Queensland
118 – 130 CRM
12
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

From the moment you sow and throughout germination and establishment,
you can rely on the performance of GAUCHO ® Insecticidal Seed Treatment
to optimise the productivity of your crop. GAUCHO protects each and every
seed and seedling from a range of established pests of summer grain crops,
and because it reduces the need to spray, earthworms and other beneficial
species can flourish. You’ll end up with more productive crop sooner, and
because GAUCHO is applied professionally and delivered on seed you’ll
also benefit from exceptional convenience and peace of mind. Simply order
GAUCHO when you order your seed. And then watch your crop perform to
its optimum.
www.bayercropscience.com.au
Bayer CropScience Pty Ltd 391–393 Tooronga Road,
Hawthorn East, Vic. 3123. ABN 87 000 226 022.
Technical enquiries 1800 804 479
Gaucho ® , Stress Shield Inside ® and logo
are registered trademarks of Bayer.
®
RRA/BAY5914

Planting the crop
When to plant
The decision of when to plant should be based on
suitable soil temperature in combination with the
last expected frost, a full profile of moisture
particularly for dryland production, avoiding
flowering during expected peak temperature
periods and therefore working back to a suitable
planting date. Consequently on a late plant try and
coincide flowering after the main summer heat
but early enough to beat the first expected frost.
Later planted crops are subject to higher insect
and disease pressure.
Early planted corn shades the soil earlier in the
season, thus reducing water lost to evaporation;
it also reaches the most critical stage of silking
with more water left in the subsoil along with a
deeper root system capable of extracting more
available water.
Soil temperature
Even though corn will germinate when the soil
temperature reaches 10 0 C it is unadvisable to plant
until the ground temperature reaches 12-14 0 C at
9am at a depth of 10cm for at least three or four
consecutive days. Even at 12 0 C corn will take up to
two weeks to emerge and the longer it takes the
more prone the seedling is to insect attacks and
damping off diseases.
The young corn plant will tolerate light frosts so long
as the growing point is still below the soil surface
which is about the six to eight leaf stage. Leaves will
still be burnt off but will be quickly replaced with
new leaves. If a frost affects the growing point it will
normally tiller and will require a replant.
An early frost on late planted corn can have a major
effect if it is severe and the crop is not at physiological
maturity (black layer).
Planting equipment
Precision planters are the main type of planters
used in the corn industry today with very little use
of traditional combines or seed drills where fluted
rollers and coulters give uneven seed distribution.
Generally speaking, compared to other grain
crops, corn is planted at a much lower population
and therefore it is crucial to have even plant stands
which can be achieved with precision planters.
Corn also does not compensate by tillering like a
crop of sorghum so it is essential to get an evenly
spaced crop.
Other advantages of precision planters are the
even planting depth, ability to apply starter fertiliser
away from the seed, insecticide boxes and spraying
equipment on the planter means that both insecticides
and herbicides/liquid fertilisers can all be applied in the
one operation. All precision planters are fitted with
press wheels which enhance seed soil contact.
New growers without adequate planting
equipment or growers not using precision
planters should consider using a contractor
with a precision planter.
Planting speed has an impact on the spacing of the
seed and the slower the better. Ground speeds of
5-6km/hour are ideal, causing less seed bounce than at
speeds of 8-10 km/hour.
14
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn
A precision planted corn crop.

Planting seed
Planting seed varies from year to year because of
seasonal influences and growing conditions. Pacific
Seeds’ planting seed can be bought in six different
categories – small flats, small rounds, medium flats,
medium rounds, large flats and large rounds all in
72,000 kernel bags.
Most vacuum planters have a tolerance to a range
of seed sizes but it is advisable to keep on hand a
range of planting plates as your favourite size may not
always be available.
The same seed size can vary in kernel count
per kg from year to year so air pressure on vacuum
planters should be adjusted accordingly.
Planting depth
Under ideal conditions a range of 3cm to 6cm is
recommended although if soil temperatures are
relatively warm corn will still emerge from a depth of
up to 9cm if moisture is available. Growers in
the southern areas who water up as opposed to
planting into pre watered fields do not need to plant
at this depth and may choose to put the
seed in at about 2-3cm.
Row spacing
Most irrigated crops are planted in rows ranging from
76cm to 100cm with the majority of planters set up
for 90cm row spacing. It is generally agreed under
irrigation and higher yielding situations, the narrower
rows have a slight yield advantage. A new concept of
putting an extra row in a two metre bed is still being
evaluated and the verdict is still out although early
results are encouraging.
On the other hand in more marginal dryland
conditions wider rows or a skip row configuration
have shown yield responses in some years. Single skips
on 75cm to 1m rows have shown some advantage
(keeping the same population as a solid plant).
Whereas double skip rows 1m row spacing are too
wide with moisture still left at the end of the season
between the rows. Double skip rows on 75cm spacing
are worth looking at in these marginal areas.
We would suggest growers try for themselves
different row configurations before looking into one
pattern as you will see different results between
hybrids and different seasons.
Plant populations
Corn grown in Australia is planted under a huge range
of conditions from the high input full irrigation areas
of southern Australia to the very marginal dryland
areas of central Queensland. As a result planting rates
vary from 100,000 kernels/ha down to 20,000
kernels/ha depending on environments and conditions.
The result of poorly spaced seed
The total water usage in a corn crop is not directly
related to plant population as water is lost by both
plant respiration and also by direct evaporation
from the soil. Until the canopy shades the total
ground you will see losses occurring to evaporation
which certainly supports the practice of wider rows
with irrigation.
Higher plant populations shade the ground earlier and
reduce the amount of water that is wasted by direct
evaporation while the surface is moist. With higher
populations plants shade each other more which
reduces the leaf temperatures and cuts down on the
amount of water transpired by the leaves. On the
other hand it does not support some of the findings
with our more marginal dryland areas in regards to
skip row configuration.
The primary function of a corn canopy is
to intercept light. Light that reaches the soil
surface is lost, or worse still reduces potential
photosynthesis and hence yield (latitude and
therefore day length is now becoming increasingly
important). Once light is intercepted it must be
used as efficiently as possible and this is a function
of leaf angle. Flat horizontal leaves do the best job of
intercepting light but use it least efficiently. Vertical
leaves are poorest at intercepting light but use it
most efficiently. The ideal plant type would have
horizontal lower leaves and erect upper leaves.
The physical makeup of the plant has told us that
with an established population of over 60-70,000
plants/ha competition for light becomes just as
important as moisture and nutrient availability.
This is one of the main reasons why we see barren
plants in higher population crops and especially with
hybrids that have more horizontal leaves rather than
vertical leaves.
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 15

One of our former hybrids, DK689 did not tolerate
high populations, in fact under irrigation its yield
declined over 60,000 plants/ha, and part of the
reasoning is that it has broad horizontal leaves.
On the other hand the newer and quicker hybrid
Hycorn 533 has no yield reduction if all other
factors are equal with populations exceeding
90,000 plants/ha and again partly due to having more
vertical top leaves.
In summary calculating the correct desired plant
population should be based on the following variables
– the selection of individual hybrid (this may also
influence row spacing and as a guide longer season
hybrids require less plants than shorter season
hybrids), the market you are aiming at (slightly
lower population will give a bigger kernel for the grit
market, silage growers may look at a few more plants
for higher dry matter production), latitude, climate
and planting time.
Remember when doing the final calculation to
determine the planting rate to achieve the desired
established plant population you need to allow for:
4 actual seed germination
4 is the soil temperature and moisture optimum
4 are there any ground insects present
4 type of planter being used and its accuracy
4 ground speed of planter.
Seed rots and seedling blights
Germinating corn seed may be attacked by a number
of soil borne or seed borne fungi that cause seed rots
and seedling blights. These diseases are prevalent
in poorly drained, excessively compacted or cold
(less than 10-13°C) and wet soils. Disease severity
is affected by planting depth, soil type, age and
quality of seed, mechanical injury to the pericarp and
genetic resistance to infection. Sweet corn is more
susceptible than field corn. The main fungi
involved are (Pythium), the rotted area may be
dark with sporangia and oospores in the tissues;
(Diplodia), whitish-grey; (Fusarium), white to pink or
(Penicillium), bluish mycelium and masses of spores.
Stalk and root rot diseases
Stalk rots are diseases that are most commonly
expressed as plants reach maturity. Corn stalk
rot (pictured below), tends to be a complex of
several disease causing fungi and sometimes bacteria,
seldom will only one casual organism be isolated and
identified. Plants with rotted stalks almost always have
rotted roots as well. Usually, but not always, the same
casual organisms are involved. Visual identification is
very difficult; typically wilting is the first sign of stalk
rot in a field. In a few days leaves turn a ‘frosted’ grey,
ears droop and the outer rind of the lower stalk turns
brown. Fields where stalk rot is developing should be
harvested early to reduce grain losses.
As a guide a reasonable field establishment is about
80% which allows for actual seed germination (let’s
say 90%) and 10% loss for the other variables.
Diseases of a
developing and
mature corn plant
Ever since the 1930s when corn was converted
from an open pollinated species to a hybrid, disease
resistance has been a high priority for breeders
around the world. Most of the corn diseases in
Australia are influenced by seasonal conditions causing
stress on the plant, such as very hot spells during
grain fill, continued cloudy weather, build up of virus
spreading insects and high humidity.
Often, like nutrient deficiencies, diseases are hard to
positively identify in the field and may need to be sent
to a plant pathologist for identification, particularly
the cob and stalk rots.
In nearly all cases of stalk and cob rots it can be
traced back to a period of stress at a crucial stage of
development, such as being a couple of days late with
a crucial watering.
Bacterial stalk rot
16
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

Ear and kernel rots
These rots can affect ears or kernels reducing test
weight and grain quality. Some rots are responsible
for development of mycotoxins that may contaminate
grain. Rotting observed in the field is often due to a
complex of casual organisms, not just one. Most ear
rots are favoured by late season humidity. Infections
are increased by cob damage by birds or insects and
by stalk lodging that allows ears to contact the soil.
Growth stages during which symptoms generally
appear are listed after the disease name and are
described as follows:
Stage I represents emergence to knee high
Stage II represents from knee high to tasselling
Stage III represents from tasselling to maturity.
Rots of stored grain
If grain is stored at between 15-20% moisture and
between 21-32°C temperature there is a higher
probability of grain rots developing. On the other
hand grain moisture of below 15% and temperatures
of below 10°C pose little risk of damage from fungi.
Storage rots are caused by many fungi, but mainly
species of Aspergillus and Penicillium.
Ruptured kernels will sometimes attract some species
of Fusarium, another good reason to set the header
up correctly to avoid broken or damaged grain.
Invasion of whole kernels in storage results in
discoloration, heating, caking and mustiness. One
storage rot, known as ‘blue-eye’ is characterised by a
bluish-green germ.
Mycotoxins and Mycotoxicoses.
Mycotoxins are fungal metabolites that are toxic
when consumed by animals or man. Mycotoxins can
accumulate in maturing corn standing in the paddock
or in grain during transportation and storage under
conditions of moisture, humidity and temperatures
favorable for growth of the toxin-producing fungus
or fungi.
Diseases in animals and man resulting from
the consumption of mycotoxins are termed
mycotoxicoses.
The effects range from loss of appetite, feed
refusal and decreased feed efficiency to mortality
in domestic animals.
Three genera of fungi – Aspergillus, Penicillium and
Fusarium – are most frequently involved in cases of
mycotoxin contamination in corn. Aspergillus flavus
produces aflatoxins in corn starting at a moisture
content of about 18% and at temperatures of between
12 - 42°C (optimum 25-32°C).
For more details on mycotoxins please go to the
Association’s website www.maizeaustralia.com.au and
look for Barry Blaney’s findings & recommendations on his
paper Managing Mycotoxins in Maize.
Harvesting
and storage
Most corn grain contracts stipulate a maximum
of 14% moisture which is normally reached about
130-150 days after planting depending on location and
time of planting.
When the crop reaches physiological maturity or black
layer, the grain moisture is about 28-34% moisture
(ideal for high moisture corn – dealt with in the next
section) and this is approximately 60 – 66 days after
silking. Dry down after reaching black layer can vary
from 0.5% up to 2% moisture per day for early planted
crops maturing during January-February in heat wave
conditions. However during the cooler and often
wetter winter months corn does not come down in
moisture much below 16% until the weather starts to
warm again (more of an issue with later plants).
As a guide the softer endosperm types and
particularly the loose husk covered hybrids dry
down quicker than the tighter husk covered harder
endosperm types.
Sometimes a decision has to be made if stalk rot is
causing some lodging whether to harvest early and
dry the grain (even though at an additional expense)
or to leave it to the optimum moisture but risk much
higher field losses.
Grain harvesting is normally done with a corn front
with either a snapper front which only removes the
ear and takes very little plant material through the
header or the other front commonly used is a cutter
bar where chains feed the crop on to the cutter bar.
Dryland growers with lower yielding crops will also
use sunflower trays which divide and guide the crop
onto the cutter bar just like the previous type but
they are not as efficient in high yielding crops.
As in planting the crop, ground speed is important
as it affects the intake grain quantity. Too much
means grain losses over the top sieve. It is also
recommended that the header manuals are followed
for setting up the header as far as drums, rotors
and cylinders are concerned. The optimum cylinder
speed for corn is usually about 350 to 450rpm.
Rotor speeds should be as fast as practical without
cracking the corn.
Concave settings are also important and as a guide
the clearance at the back of the concave equals the
diameter of the cobs.
Not only will a poorly set up header crack grain but
with some of the specialty corns like gritting corn for
grit manufacture and pop corn they can cause hair
line stress fractures which most contracts only accept
minimum damage. Post harvest handling of this type of
material is also crucial as augers can be very abrasive
and will have the same effect as will grain falling from
a great height into silos.
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 17

Harvesting corn
Stress fracturing will happen with standing crops
in the paddock as well, particularly the harder
endosperm types with little tip coverage, looser husk
cover and quicker dry down. Also in the autumn if the
difference between night and daytime air temperature
is more than 30°C.
Incorrect artificial drying can also cause stress
fractures either due to excessive heat (above 50°C)
trying to dry too quickly or the grain is allowed to
cool down too quickly with very cold outside air.
Corn at 15-16% moisture can be stored over the
cooler months using aerators but once the weather
starts to warm up it will need to come back to 14%.
Like all stored grain (for that matter standing crops,
particularly late ones) insects will attack them,
particularly in humid conditions, so attention needs
to be given if storing for a period of time to apply
insecticides or insectigas.
For more details on standards please refer to
NACMA Standards on the Association’s website
www.maizeaustralia.com.au
Other uses of corn
for livestock
Corn for silage
Corn silage is a form of fodder conservation, of which
there are many types ranging from baled straw, hay,
grain through to fermented forage to produce silage.
History has taught us to prepare for the lean
times by saving in the good times and the same
principal applies to fodder conservation in that we
conserve fodder in the good seasons to prepare
for times of drought or to supplement in times of
lower quality pastures.
Silage, whether it be corn, forage or grain sorghum is
different from most of the other basic forms of fodder
conservation in that it is a much better quality feed.
As a result corn silage in particular is a permanent
part of a lot of both dairy and beef feedlot rations.
Why is corn silage the most widely grown fodder
crop around the world
4 It is a very palatable or digestible forage (usually
above 70%) with relatively consistent quality.
4 Corn crops produce high yields, both grain
and dry matter with good levels of energy
(9.5 – 11mj/kg) compared to most other forages.
4 Less labour and machinery costs are involved
with corn silage compared to other harvested
forages because it only requires a single
machinery pass.
4 The cost per tonne of corn silage also tends to be
lower than for other harvested forages.
4 Relatively cheap forms of storage can be built or
used – stack silos, bunker silos, pits, round or
large square bale silage, sausage bags to the more
expensive upright sealed silos.
However corn silage is inherently low in
protein (4 – 8%) and some minerals so it should
not be used as a straight substitution in feeding
regimes. The other negative with corn silage is
machinery needed for feeding out and the limits of
transportation over distances.
High moisture grain
In recent years, storage and feeding-out of high
moisture corn is proving popular with some of
the bigger feedlots and dairies as an alternative to
dry corn.
Basically what is involved is harvesting normal field
corn (usually the softer higher yielding hybrids) with
a normal header at an optimum moisture content
of 28-32%. This moisture content coincides with
black layer and at these percentage shells from the
cob nearly as well as dry corn. Unloading with thin
diameter augers will create some problems, so it is
advised where possible not to use them.
18
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

After the corn has been harvested it is normally
tub-ground (to allow microbial activity to work more
quickly on the fermentation process and cracked
grain is digested better by livestock) and then ensiled
into a pit, bunker or sealed upright silo. In the case
of a pit or bunker it should be rolled just like silage
to exclude air (anaerobic environment) so proper
fermentation can take place.
Harvesting at the correct moisture, cracking the grain
and correct rolling, goes a long way to ensuring a
quality product with very little wastage.
High moisture corn grain offers a few advantages over
normal dry grain:
4 Harvest earlier (normally at least a month earlier)
without having to wait for slow dry down in late
autumn/ winter. Rain is really only a hold up until
the ground holds the machinery. This early harvest
may give the opportunity to double crop.
4 Reduces field losses due to cracking and usually at
this stage there is no lodging.
4 Relatively low cost storage.
4 High moisture corn has a feeding value similar or
slightly better than dry grain when fed on an equal
dry matter basis.
Because of the moisture difference it is worth
remembering that each 1kg of dry corn (15%
moisture) is equal to 1.2kg of high moisture corn at
30% moisture.
Corn Earlage
There has been a lot interest of late where just the
cob and husk cover are ensiled by using a snapper
front on the chopper. The crop is chopped at 35-40%
moisture or in other words in maturity between the
silage of whole crop and a crop taken at the high
moisture stage.
The resultant silage gives a very high energy feed value
and has obviously a higher fibre content than that of
straight high moisture grain.
Intensive livestock operations that are using corn
earlage are finding they can feed a high percentage of
their ration with this one product.
By taking just the cob for earlage means harvesting
earlier and you are able to return a lot of organic
matter into the soil as opposed to taking the whole
crop for silage. When chopped the material is treated
just like whole crop silage as far as ensiling it in a pit
or bunker.
Alkalage
Alkalage is the preservation of whole crop
(grain and stover) or part thereof by the process
of ammoniation (the addition of soybean based pellets
containing urea and urease enzme) - rather than a
process of fermentation as with silage.
The process, involving a precision chopper with a
grain processor but shorter chop length is particularly
suited to mature crops of winter cereals, sorghum
and corn with a dry matter range of 65 to 85%, or
less than 35% moisture. For more details, refer to the
forage agronomy guide.
Understanding the fermentation process
Silage is different from other forms of fodder
conservation in that it converts forage into silage
through a process called fermentation. Basically, the
plant sugars are converted by anaerobic (oxygen free)
bacteria into acids (predominantly lactic acid) which
reduce the pH of the plant material and therefore
preserves the crop.
The best quality silage results when lactic acid is the
dominant acid as it is the most efficient fermentation
acid and will drop the pH of the silage the quickest.
Harvesting corn for silage
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 19

Under proper ensilaging conditions corn silage will
normally ferment quickly to a stable pH of about four
within the first week.
The major chemical and microbiological changes
which occur during fermentation are:
4 Aerobic phase – the timespan from cutting to
ensiling the crop should only be a few hours. The
aerobic phase reduces silage quality and should be
minimised as plant sugars are lost to respiration,
produces heat and promotes aerobic microorganisms
(yeast, moulds and aerobic bacteria).
With poor management – crop too dry, poor
chop length, slow filling, poor compaction or not
covering silo will result in aerobic phase continuing
for several weeks.
4 Anaerobic fermentation phase – after the crop
has been ensiled, rolled and covered (oxygen
depleted) anaerobic bacteria ferment the
sugars which are converted primarily into lactic
acid. The production of acid lowers the pH of
the ensiled crop which inhibits the growth of
other microbes.
In corn silage the active anaerobic fermentation
process generally lasts less than a week. The rate
of fermentation depends on the quantity and
type of lactic acid bacteria present on the crop
at ensiling and the moisture content of the silage.
Wetter forages ferment faster than drier ones.
4 Storage phase – If ensiled properly the pH of the
ensiled material remains fairly stable and there
is minimal microbial and enzymatic activity if the
ensiled crop is kept anaerobic. If oxygen is allowed
to enter silos at this stage quality can be reduced
by increases in moulds, yeasts and an increase in
heat. Also, poor drainage, leaking walls or holes
in the covering surface will increase spoilage or
wastage.
4 Feed out phase – The feed out phase begins once
the storage is opened and continues until the
silage is consumed. Once silage is re-exposed to
oxygen, yeasts and moulds become active again
producing carbon dioxide, water and heat. Besides
the loss of digestible nutrients, some moulds can
produce mycotoxins which can cause illness or at
least a reduction in intake and therefore livestock
performance.
At feed out, removing silage from the pit face at a
rate of at least 2-3cm per day reduces losses due to
poor aerobic stability. Pit design and size should be
matched with the feeding rate in order to minimise
silage loss during feed out.
Pit face management is also important in managing
aerobic deterioration in silage. Maintaining a firm,
even and a clean face on pits will help minimise losses.
Tips for making better
quality silage
Growing the crop
First set a realistic yield goal and as a guide for
irrigation you should be aiming for 17 to 25t/ha DM,
favourable dryland 15 – 20t/ha DM and more marginal
dryland 10 – 15t/ha DM.
Treat a corn crop intended for silage the same way
you would a grain crop but remember that you are
taking the whole crop and returning no nutrients to
the soil, so make sure you adequately compensate in
your fertiliser program, particularly with nitrogen and
potassium (refer to earlier section on nutrition).
Only plant hybrids that are well suited to your
area and which have a good grain yield potential.
Remember that the grain yield should make up
approximately half of your total silage yield and the
other half is made up of leaves and stalk (stover). So it
may be tempting to plant a tall long season hybrid, but
unless you can achieve roughly a 50% ratio of grain
and stover you will affect quality (energy). Stay-green
is also a worthwhile characteristic to consider when
choosing hybrids as it means you have a slightly longer
chopping window, particularly in the heat of the
summer. Of course it is important to select hybrids
that have good disease resistance.
If planning to grow a large area of silage it is worth
considering either mixing your maturities up or
planting over a period of time so the whole lot does
not come in at the one time. This is very important
on the early plant when harvest will be during the
middle of the hot summer.
Some people advocate planting silage corn at a rate
10% higher than corn grown for grain. Pacific Seeds’
agronomy staff believe it depends on the hybrids, as
an increase in population may give an increase in
dry matter production but could also give you a
reduction in grain yield with many hybrids. As a
guide the quicker maturing hybrids respond better
to higher plant populations than do the longer
season hybrids.
Harvest timing is crucial
All of the work invested in growing a good crop
can be undone if it is not harvested at the right time
or correctly.
A corn plant has its maximum dry matter weight
when it is approximately 35% DM or 65% moisture.
Coincidentally, at 30 to 35% DM it is nearly ideal for
fermentation and compaction of the forage in pits.
Actual moisture at harvest time will be determined by
the type of storage you have:
20
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

4 above ground bunker or stack silos
– 67 to 72% moisture or 28 to 33% DM
4 below ground pits
– 64 to 70% moisture or 30 to 36% DM
4 upright sealed silos
– 50 to 60% moisture or 40 to 50% DM.
If the corn crop is harvested at above the desirable
moisture content the plant will not have reached
its maximum dry matter production, kernels will be
more sugary than starchy, the chop length will have
to be lengthened and there will be more seepage of
nutrients from pits.
On the other hand if the crop is drier than
desirable you will end up with more field losses,
the plant has passed its maximum dry matter weight,
chop length will have to be shortened, compaction in
the silo or pit is more difficult, more aerobic effects
due to air pockets and the fermentation takes longer
resulting in more wastage and reduced quality.
A system of scoring the milk line on kernels is the
most practical way of determining the approximate
moisture of the crop. Ideally, a milk line score of 2.5
to 3 out of five is ideal timing for cutting the crop for
most pits, stacks and silos. It usually takes about 20
days from when the milk line (or starch line) starts at
the top of the kernel and works its way down to the
tip (black layer or physiological maturity). This will
vary depending on the time of the year and especially
during very hot, dry weather where it may only take
15 days. It is during this period you need to regularly
check the crop and make sure you have either your
own machinery ready to go or have your contractors
ready at the gate.
Once you have started chopping the crop a simple
squeeze test will give you an indication of the
moisture. If you can just make juice run, after
squeezing firmly in the hand, then it is about
68-70% moisture.
The other test involves drying a sample in a
microwave oven to determine the moisture content
– place 100gms in the microwave with a container
of water beside it on high for four minutes, weigh it,
dry it for another minute, re weigh it and continue
to repeat until the weight does not reduce anymore
(be careful it does not burn). The resultant weight is
the dry matter weight. Use the following formula to
determine moisture content.
Moisture content =
(1 - (dry matter weight/wet weight)) x 100
Harvesting the crop
Once harvesting commences it should be all
hands on deck to try and gain the maximum quality
from the crop while it is at the ideal stage and to take
the least time possible to harvest the crop, transport
it to the storage area, roll it and seal it.
Critical inspection periods
MAIZE CROP GROWTH STAGES
Pollination
20 leaves
Tasseling/silking
15 leaves
Silage harvest Grain harvest
Physiological maturity
2 leaves
fully
emerged
Emergence
5 leaves
fully
emerged
Tassel and ear
initiation
8 leaves
fully
emerged
12 leaves
Planting
Days -9 -3 0 7 21 35 46 56 63 100 118 150
Pre-plant Avoid spraying Post-emergent Highest water and nutrient requirements
Harvest aid
application
Avoid spraying during pollination
Pre-emergent
application
Wireworms
African black beetle
Critical thresholds
one per sqm. Visible plant loss
Cutworms
Armyworms
10% defoliation per plant
Heliothis
Eggs and larvae on tassels and silks
Monoleptra beetle
Silk damage
Mites
Australian Maize Kondinin Group Figure 1
kernel
tip
1 2 3 4 5
Maize Growing NSW Agriculture Agfact figure 2
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 21

The harvest needs to be coordinated in such a
manner that there is no delay with either the
chopper or trucks unloading at the storage site. Any
breakdowns will slow the whole process down and
eventually reduce quality so good maintenance on
machinery should be done well in advance and should
be thoroughly checked every night or in the morning.
Particular attention should be given to making sure
the chopper knives are sharp otherwise efficiency is
reduced and blunt knives will fracture the cells of the
plant, thus releasing the juices adding to seepage.
If the harvest is delayed by some time due to
mechanical breakdowns or wet weather you may have
to mix some wetter fields in with corn that is just past
optimum. The optimum chop length is 10 to 20mm
but if the crop is drying down quickly you may need
to shorten the length to 5mm.
Silage Inoculants
Bacterial silage inoculants are often added as a form
of insurance to improve efficiency to the fermentation
process (increases lactic acid which reduces the pH
rapidly and stabilises the silage quickly).
There is a move in more recent times to using the
newer live bacteria culture which actually multiplies
once put into the tank on the chopper.
Using an inoculant that also contains the bacteria
Lactobacillus buchneri will help alleviate secondary
fermentation in the pit and during feed out by
reducing the build up of heat.
Filling and packing the storage
Good forward planning is obviously required for an
efficient storage system to meet your requirements
and budget. For bunkers and stacks first of all select a
good site with a slight slope for drainage and for pits
preferably on the side of a hill, but not too steep for
manoeuvring machinery. Good clean straight walls
are better and obviously not in sandy soil. Close
proximity to the feed out area is also advisable.
If the corn silage is being stored for a long period
as a drought reserve, then the size of the storage is
not as important as a short term proposition. For
short term storage you should work out even
before you plant the crop how much silage you
need for your operation to start with, then plant
the desired area (remember to allow for about
15% wastage overall – harvest losses, spoilage and
feed out losses, this figure could be higher depending
on management). Finally match up the storage area
with the anticipated yield and requirement.
Remember that freshly cut corn silage has an
approximate density of 350kg/m 3 whereas properly
compacted corn silage has a density of approximately
700kg/m 3 or 1.4m 3 / tonne. From this information you
can calculate the dimension and size of your stack
or pit. They need to be at least two tractor widths
so the centre is properly rolled and preferably the
biggest tractors for better compaction.
With pits and silos do not spread the fresh forage
along the entire length at once as there will be too
much surface exposure to the air. Fill and pack the
whole storage as quickly as possible to again avoid
negative aerobic activity.
The design of the pit or stack should allow the face
moving at a rate of 150mm/day so as to reduce
aerobic losses. Consideration needs to be given
to the height in respect to available machinery for
feeding out.
Covering or sealing
On completion of rolling the silage care should be
taken to properly cover the silos with heavy plastic
sheeting to eliminate exposure to air and rain. Old
rubber truck and four wheel drive tyre splits are
popular for weighing down the plastic and loose
forage or soil can be used on the edges to properly
seal it. For longer term pits a layer of soil rolled will
do the job.
As the corn is harvested and the collector bin filled,
another waits in the background
Compacting silage in a pit
22
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn

Silo gases – DANGER!
The fermentation of green plant material
produces nitrogen dioxide and on contact
with water or fluid (lungs) turns into highly
corrosive nitric acid.
It is odourless, colourless, and tasteless and
is 53% heavier then air.
This is more of an issue in upright sealed
silos, so make sure it is well aired if you
have to enter the silo.
Secondly, when removing the material from the pit
face be careful not to disturb the surrounding material
or secondary fermentation will take place including
heating up.
Unloading silage into a pit
It is important to regularly check for holes in the
plastic and repair them to reduce losses.
It may seem like a lot of extra work covering the
silage but it is worth it in the long run with the
reduced wastage.
Feeding out
If all steps have been followed in ensilaging the
corn crop, fermentation should be complete in
14-28 days and will then be ready to be fed out.
The addition of silage inoculants will help reduce
the fermentation period.
All the work of making good silage may be brought
undone if proper pit and face management are not
adhered to.
Firstly, when designing the pit it should have been
taken into consideration to get right across the pit
face at least every two to three days.
Several attachments are available for the front of
tractors including buckets, silage grabs and insulators.
The silage is then usually put into a wagon or cart if
feeding straight silage or into a mixer if other grain
and additives are to be used.
Feed troughs or pads are advisable to reduce wastage,
spoilage and trampling.
Ethanol production
With increased interest in using ethanol as a
fossil fuel substitute, corn is a grain source that is
used substantially in the USA for this purpose. The
process of ethanol production from grain starch
involves milling, fermenting and distillation of the
ethanol and corn is a very good raw material source
because of its high starch content. The two significant
and valuable products from this process are ethanol
and wet or dry distillers grains (with protein of
about 25%).
Pacific Seeds’ hybrids are extremely suitable for
ethanol production.
Feeding out silage in a trough
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn 23

Summary
How to grow a 15 t/ha grain or a
85-90 t/ha silage crop of corn
A combination of good luck and good management is
required to achieve a high yielding corn crop. Firstly,
we need to accept the individual growing environment
and unless you are situated in a favourable one you
are behind the eightball to start with. Just refreshing
the memory on the perfect environment – lower
than 23°S latitude, an elevation of above 1,000m,
deep, well drained soil and preferably not too high
a clay content, summer time temperatures of 24-
30°C with a reliable water supply or rainfall. On the
other side of the ledger a high yielding corn crop
also requires a high level of input management to be
assured – selecting the correct hybrid, planting at the
correct time and population, proper crop hygiene
implemented for weeds, insects and disease, correct
amount of nutrition applied and above all else good
water management particularly during the crucial
usage period. Even with good management it still does
not guarantee a high yielding crop of corn if extreme
climatic conditions are experienced during the crucial
pollinating/grain fill period as has been the case during
the early part of this century.
PACIFIC SEEDS NUMBERING SYSTEM
Hycorn & Pac Hybrid Type Maturity CRM Hybrids CRM
Number Series
M500 - M529 Quick Feed 95 - 104 DK 477 97
Hycorn 504 97
Hycorn 502 IT 104
M530 - M599 Med-Quick Feed 105 - 112 Pac M533 109
M600 - M699 Medium Feed 113 - 120 Hycorn 424 115
Hycorn 675 IT 118
M700 - M899 Hard/Grits 110 - 120 XL 80 118
Hycorn 345 119
Pac M712 118
Hycorn 345IT 119
Hycorn 727 123
M900 - M929 Temp X 121+ Hycorn 901 126
Tropical
M930 - M959wx Waxy 105 - 115
M960 - M969W White 110 - 120 DK 703 W 120
M970 - M979pop Popcorn 110 - 120 Burst 115
* Hybrids released from 2003 onwards come under the current numbering system, hence Hycorn 424 not
beginning with a 6 or 7 prefix for example. Also Pacific Seeds has the marketing rights of Dekalb in Australia,
hence the prefix DK on some hybrids.
All of the information in this document is subject to copyright. No part of this document may in any form or by any means (whether electronic,
mechanical, or otherwise) be copied, reproduced, stored in a retrieval system, transmitted or provided to any other person without the prior written
permission of Pacific Seeds Pty Ltd, who owns the copyright. The information provided in this brochure is intended as a guide only. Various factors,
including planting times and environmental conditions may alter the characteristics of plants.
24
Pacific Seeds Yearbook 2008/2009 - Hybrid Corn