CORN NUTRITION GUIDE

FIELD
CORN

pacificseeds.com.au
CORN HYBRIDS
CONTENTS

Corn nutrition 1
Nutrient removal 3
Role of nutrients in corn 5
Nitrogen 5
Nitrogen fertiliser strategies 7
Phosphorus 11
Phosphorus fertiliser strategies 12
Potassium 13
Potassium fertiliser strategies 14
Sulphur 15
Sulphur fertiliser strategies 16
Zinc 17
Zinc fertiliser strategies 18
Comment: Effective use of recycled bio-solids 18
References 19
 CORN NUTRITION
Corn is recognised as a high yield crop provided optimum crop management is used. Yield potential
of corn is essentially dependent on the amount of intercepted radiation, water and nitrogen available,
moderated by factors such as temperature and radiation intensity. The production, retention and function
of leaf area is the key to productivity and adequate plant nutrient supply at all stages is vital in this process.
High yielding corn crops require nutrient availability in both total quantity and timing. Rates of fertiliser will
vary depending on factors such as locality, soil fertility, previous crop, fertiliser history and yield potential.
The nutrients that most frequently limit production are nitrogen (N) and phosphorus (P). Sulphur (S),
potassium (K) and zinc (Zn) may also be limiting in some soils or under some growing conditions and in
some soil types.

Crop Uptake
Corn has a high demand for nutrients. For each tonne of yield, a corn crop requires defined quantities
of nutrients. Nitrogen (N) and potassium (K) are nutrients required in the greatest quantities followed by
sulphur (S), phosphorus (P), calcium (Ca) and magnesium (Mg). Total uptake for each nutrient can be
calculated by multiplying the nutrient uptake in Table 1 by the grain yield (t/ha). The amount calculated
also represents the quantity of nutrient likely to be removed if the crop was to be harvested as silage
(typically 20- 25 tonnes/ha DM) or hay.

Table 1 Typical nutrient uptake for most commonly applied nutrients in corn
Nutrient N P K S Zn
Uptake 22-30 kg/t 4.5 kg/t 16.3 kg/t 5.2 kg/t 24 g/t

The timing of nutrient demand in corn is similar to other cereals with K and N occurring ahead of dry
matter accumulation and phosphorus uptake. Corn takes up 75% of its nitrogen requirement in the
vegetative period prior to tasselling. A shortage of nitrogen during this period significantly reduces growth
in stems and leaves and consequently in the number of grains produced, and so leads to reduced yield.
The remaining nitrogen taken up between flowering and maturity is important for maintenance of grain
number, achievement of grain size and protein content. Fifty percent of its K requirement is during the
vegetative period prior to floral initiation, while the uptake of P peaks at early flowering, with 45% of the
total P demand being taken up during booting and flowering (Figure 1).

Minor variations to this pattern may result from differences in the degree of multiple cobbing between
varieties. Multiple cobbing generally extends the uptake period for all nutrients.

Double cobbing corn, typical of some hybrids planted at low populations.

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Figure 1 Nitrogen, phosphorus and potassium uptake patterns
for an 11t/ha grain corn crop (Purdue University 1995)

350.0 25000

300.0
20000

250.0
Nutrient uptake (kg/ha)

Shoot DM (kg/ha)
15000
200.0

150.0
10000

100.0

Late silk Grain Fill Black layer 5000

Tassel Blister
50.0
Shoulder high
Seeding 4 leaf 9 leaf
0.0 0
02 04 06 08 0 100 1201 40

N P K Shoot DM Kg/ha)

The demand for N varies more widely than for other nutrients being dependent on the grain yield and
grain protein content. Crop N supply is related to the grain protein content (kg N/t) and the N efficiency
at which soil and fertiliser N is taken up and transferred to grain. The N supply required to produce a
range of yield and protein levels is given in Table 2.

Table 2 Crop N demand required from all sources required for a range of grain yield and protein targets.
(Based on the relationship between maximum yield and associated grain N % of Steele et al 1982,
Wortmann et al 2011)

Target grain protein typical economic

Target grain protein max yield (%)
optimum yield (%)

Target yield (t/ha) 8 9

1 26 29
2 51 58
3 77 87
4 102 115
5 128 144
10 256 288
12 307 345
15 384 432
18 460 518

2
 NUTRIENT REMOVAL
With soils in many corn growing regions now exhibiting responsiveness to a wider range of nutrients,
the starting nutrient rate for crop nutrition strategies is frequently replacement of that removed in the
grain. This can be based on published typical nutrient removal rates such as those in Table 3, or can be
related to removal measured at a farm or paddock level by measuring grain nutrient content. This can
be done by submitting a representative sample of grain for a complete plant tissue analysis. The range
in removals displayed in Table 3 were collected from grain samples collected from a range of reference
sources both local and international with a large range of growing conditions, varieties, soil and fertiliser
regimes.
The range suggests that some investigation of removal at a paddock level is likely to improve calculation
of appropriate maintenance rates.
Table 3 Typical nutrient removal (kg/t for NPKS and g/t for Zn) for most commonly applied nutrients in
corn

Nutrient N P K S Zn
Removal 15 2.9 3.3 1.3 18
Range 9 - 26 1.9 – 4.0 2.6 – 4.1 0.9 – 1.7 13 - 24
% of crop uptake 50 65 20 25 75
removed

A maintenance or replacement strategy is generally suitable for nutrients other than N with marginal
to adequate soil status. This is typical of situations where crops sometimes show small responses to
nutrient addition. The dynamic nature of the nitrogen cycle requires fertiliser N to be managed based
more on the seasonal assessment of yield potential and likely soil N supply.

Establishing the need for increased nutrient supply

The need to supplement the native soil nutrient supply to maximise yield can be identified using a
number of methods. Most directly via test strips and indirectly through the use of soil and plant tissue
analysis. Waiting till the onset of clear foliar symptoms can cost up to 20% yield penalty for a number
of years before the clear symptoms emerge. The yield loss that occurs before symptoms occur is
commonly referred to as “hidden hunger”.

Critical levels of important nutrients for the dominant soil types in corn growing areas are presented in
Table 4. The values are general and may vary in response to a range of other soil chemistry and biology
variables. Soil sampling depths indicated are important in ensuring the interpretability of laboratory
analyses, particularly for soil immobile nutrients such as P, K and Zn.

Table 4 General soil analysis critical values for nutrients most limiting to corn grown in summer dominant rainfall areas

Sample depth (0-10 cm)

Nutrient Low P buffer Moderate P buffer High P buffer

Phosphorus (Colwell) mg/kg 20 40 60*
Low CEC Moderate CEC High CEC
Potassium (exchangeable) cmol(+)/
0.2 0.4 0.6
kg
Low pH Moderate pH High pH
Zinc (DTPA) mg/kg 0.1 0.5 0.8
0 – 10 cm
Sulfur (MCP) mg/kg 8

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 The wide critical range for P is related to the range of early season soil temperature and phosphorus buffer
indexes (PBI) across corn growing areas.

Plant tissue analysis is generally used as a diagnostic tool where plant growth appears to be affected by
nutrient deficiency. Where used correctly it has the advantage of reflecting the root uptake-soil supply
relationship of the crop.
The values in Table 5 represent the lowest nutrient concentrations for youngest expanded blade below
which yield may be reduced.

Emerging technologies that use spectral reflectance or transmission also appear to have some application
in nutrient management of corn where in-crop nutrient application possible.

This technology is most developed for N but commercial availability of decision support in corn is
currently limited. Yara N-Sensor™ and Ag Leaders OptRX® Crop Sensor proximal sensors, SPAD
chlorophyll meter, RapidEye® Satellite Sensor and WorldView-3 Satellite Imagery are examples of remote
sensing platforms that have been developed to provide crop N status in other crops.

Table 5 Plant tissue analysis lower value of adequate range for corn (Bryson et al. 2014) for whole tops
sampled when crop is less than 20 to 30 cm high

Cu mg/
N% P% K% S% Ca % Mg % Zn mg/kg Mn mg/kg Fe mg/kg B mg/kg Mo mg/kg
kg
3.5 0.3 2.5 0.15 0.3 0.15 5 20 20 30 5 0.1

NDVI image of corn captured by drone.

GreenSeeker® in use on corn.

4
 ROLE OF NUTRIENTS IN CORN

NITROGEN
Nitrogen is a key nutrient in a large number of plant functions including being central to production
of amino acids and protein, formation of chlorophyll, is a component of vitamins and affects energy
relations in the plant.

Nitrogen stress in corn is characterised by:

• Reduced dry matter;

• A light green to yellow general colouration with spindly stalks;
• Yellowing and necrosis of lower leaves beginning at the tip and proceeding in a ”V-shaped” pattern;
• Slow growing, small cob size; and
• Low grain protein.

Nitrogen deficiency in corn, late onset, see bottom half of crop with early senescence.

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 Figure 2 shows the typical N uptake rate (N flux) pattern for a corn plant. It
appears that the plant does not use much N during the first 20 days, but by the
time the plant is 45 – 55 days it has reached its maximum N uptake rate and
by 60 days old, it has used close to 60 percent of the total N. This pattern of
uptake, the soils' ability to retain N and growing season rainfall patterns should
guide N application strategy.

N uptake

250 18%

16%

200
14%
Typical N uptake (kg/ha)

12%
150
10%

N Flux
8%
100
6%

4%
50

2%

0 0%
VE V2 V4 V6 V8 V10V 12 V14V 16 V18V TR 1R 2R 3R 4R 5R 6
Growth stage

Figure 2 Typical nitrogen flux (% total N requirement for each growth stage) and uptake patterns for corn
(12.5 t/ha yield). Maximum daily uptake rate occurs around 50 days.

Nitrogen fertiliser strategies for rain-grown crops should be based on a realistic target yield, based
primarily on stored soil moisture with some allowance for summer rainfall and previous paddock history.
For irrigated crops, the quantity of water and timing of irrigations are also influential in setting a target
yield. The grain protein content of corn and other cereals crops (Table 6) can be used as a reliable
indicator of the adequacy of available N to optimise yield for seasonally available water. Grain protein
in corn of less than 8% generally indicates that the crop would have likely yield more with increased N
availability.

Table 6 Target grain protein for yield optimisation with nitrogen for a range of cereal crop grown in rotation with corn

Crop Target Grain Protein %*

Corn 9
Sorghum 10
Barley 10.5
Wheat 11.5
* Grain moisture at delivery standard

Nitrogen fertiliser rates are generally determined for corn as part of a partial N budget. The crop N demand
is provided for a range of yield and grain proteins in Table 2. This N demand needs to be matched by a
combination of residual soil mineral N (as measured by a soil test), N released from the soil organic matter
and previous crop residues with any deficit being supplied by fertiliser N.

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 NITROGEN FERTILISER STRATEGIES

Nutrient Source
Urea, anhydrous ammonia and ammonium sulphate are the most commonly used N fertilisers applied
for corn preplant and side-dressed. Topdressing with urea and ammonium sulphate needs to be
assessed for the potential for ammonia volatilisation loss. When applied in the same soil banded or
broadcast and incorporated there is no evidence of consistent differences between the products' in crop
N response.

Efficiency enhanced fertiliser (EEF) products are designed to modify the release pattern of N from the
product to either increase synchronisation of N availability with crop demand and/or help lower the risk
of losses from denitrification or volatilisation. To date these product have been successful in reducing
nitrous oxide emissions but have not reliably demonstrated profitable and predictable dollar returns in
raingrown corn crops.

Application Rate
Raingrown generally 0 to 180kg N/ha
Irrigated generally 80 to 300kg N/ha

Application rates for specific yield and soil N availability can be calculated as the difference between a
crop's N demand (Table 2) and its soil N supply (Table 7).

Table 7 Estimated N supply from a range of soil mineral N

values for sampling 0-90 cm in a cereal based rotation

Soil mineral N mg/kg Estimated crop available N (kg/ha)

1 15
5 62
10 121
15 179
20 238
25 296

Application Method
Preplant applications are generally best banded into the soil to reduce immobilisation if high stubble
loads are still present. Nitrogen bands should generally not be placed at a greater width than plant row
spacing. For skip row configurations application bands should be placed to ensure that each row of
corn has access to a fertiliser band on at least one side of the plant row. Preplant broadcast application
without incorporation should be avoided for urea and sulphate of ammonia on alkaline calcareous soils
due to increased losses from volatilisation.

Application of N products in contact with the seed, particularly when sown at wide row spacing, should
be minimised or avoided due to the risk of reducing crop establishment (Table 8).

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Table 8 Suggested maximum rates to minimise emergence effect of fertiliser
for some commonly used fertilisers

Seedbed utilisation (SBU) factor

Product
1% 2%
Urea 5 10
MAP 30 50
DAP 20 30

SBU 1% is typical in row fertiliser concentration generated with a furrow width of

1cm on a 100cm row spacing. This data is for clay soil with good soil moisture.
For more details see Online Fertilizer Damage Tool http://anz.ipni.net/article/
ANZ-3076

When applying N post-emergence using soil disturbing bands, application depth should to sufficient to
ensure soil coverage of fertiliser in the application trench and at enough distance from the established
crop to avoid root damage. It is advisable to locate the extent of lateral root extension before
application.

Application equipment should be configured to minimise dribble banded N contacting the crop.
Liquid nitrogen product are generally sufficiently concentrated to cause osmotic burn and localised
ammonia toxicity. More extensive burn is create by inappropriate rates of N applied in foliar application

Anecdotal evidence suggests that for broadcast application, rates of urea should be kept below 100kg/
ha when crops are between growth stages 2 and 3 are in a single application to lower the risk of
fertiliser burn in the centre whorl.

Leaf burn caused by volatilisation of ammonia from unincorporated urea (12 hours).

8
 Application in irrigation water should only be attempted where water application is efficient and even.
Where logistically possible, it provides an application option that eliminates soil disturbance. Urea and
anhydrous ammonia are the most common products used for this method of application. For flood
irrigation, both urea and anhydrous ammonia can be used however there are restrictions related to
maximum rate, water temperature and length of run that restrict anhydrous ammonia’s effectiveness.
Urea and urea-based solutions are suitable for overhead and subsurface irrigation systems.
Increased maintenance of metallic components of irrigation equipment should be planned where N
products are applied via irrigation.

Application Timing
The total fertiliser N requirement is frequently applied pre or at-planting in raingrown crops due to either
unfavourable logistics of in-crop N application or unreliability of rainfall to promote efficient uptake.
Given the N uptake pattern in Figure 2, in raingrown crops the highest N efficiency can be achieved by a
split application strategy where about one-half to two-thirds of the total N applied preplant or at sowing,
the remainder applied side-dressed between the sixth-leaf (V6) to tasselling (VT) stage. Follow-up rainfall
to carry the N into the root zone is required to obtain the benefit of N applied in-crop.

For irrigated crops and high yield potential dryland crops, a three-way split, with a portion of the N being
applied at the V6 and VT stages provides added flexibility to match N supply to yield potential later in the
season. Irrigation method and frequency will have an effect on the root density and distribution in the
soil profile. Frequent surface applied irrigation i.e. centre pivot or lateral can encourage a higher density
of root growth in the surface layers, compared to limited irrigated or rain grown crops. Placement and
timing of N needs to be matched to the available water profile.

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Liquid side dress applicator. Side dressing: Single disc with anhydrous.

10
 PHOSPHORUS
Phosphorus is vital for the early development of young corn. It is involved in photosynthesis, respiration,
energy storage and transfer, cell division, and enlargement, promotes early root formation and growth, and
increases water-use efficiency.

Symptoms of a lack of phosphorus in corn includes:

• Blue green colouration with reddening of stems and lower leaves;

• Poor vigour;
• Restricted root development; and
• Delayed or uneven flowering.

Phosphorus availability to crops is controlled by the interaction of a range of soil chemical, biological and
physical parameters, in combination with weather factors such as temperature and rainfall. Corn grown
following paddy rice is especially at risk of P availability problems related to changes in soil P chemistry and
biology in soils flooded for an extended period.

Responsiveness to the addition of phosphorus fertiliser is identified by the presence of a number factors that
increase the likelihood of corn response (Table 9). Additionally, responsiveness is generally categorised as
either a “starter” or “season long” response. Starter responses are generally visible as an increase in growth of
a crop early-season that does not always increase harvest yield. Starter responses typically produce grain yield
increases of 100 – 500kg/ha. Season long responses are generally visible all season and frequently produce
grain yield increases greater than 500kg/ha and hasten flowering.

Table 9 Major contributing factors to the two types of P response

Starter response Season-long response

Cool soil temperature during crop establishment Low available P in whole soil profile
Low soil available P in surface soil Long fallow or following non-VAM crop e.g. canola
Deep sowing
Short and summer cereal to summer cereal
fallows

Response to P has been more common after long fallows. More recently it has been demonstrate that
“season long” summer cereal responsiveness to P in rain grown crops is strongly related to the P in the 10 –
30cm soil layer than 0-10cm alone. Application of P in the 15 – 25cm soil layer has been found to increase
the probability of season long responses when soil P test is low in a 10 – 30cm soil layer (Table 4).
Seasonal rainfall patterns have also been found to affect response to P. Table 10 contains modelled estimates
of the likely effect some common seasonal rainfall patterns on yield reduction from less than optimum
fertiliser P supply.

Table 10 Estimates of relative yield losses in summer cereal that could be experienced if a combination of
starter P and deep P fertiliser was not applied for different soils and season types (adapted from Zull et al. 2015)

Season PAWC Estimate of relative yield loss %

Dry start 5
Wet start, dry finish 120 mm 10
No serious water stress 15
Dry start 10
Wet start, dry finish 240 mm 25
No serious water stress 15

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PHOSPHORUS FERTILISER STRATEGIES
Nutrient Source
The majority of both dry and liquid P starter products are based on ammonium phosphates MAP and DAP.
Due to the extra ammonium molecule in DAP there is more risk of crop establishment reduction from
DAP than MAP when applied in the seed furrow.

If “starter” products contain ammonium forms of nitrogen and/or potassium the rate of application and
application method needs to be closely assessed as products will reduce crop establishment if the in-row
rate is too high.

Liquid sources of P provide a slightly lower risk of crop emergence damage at equivalent rates of dry
granular P, and may have some logistical advantages but have failed to demonstrate superior responses
for an equivalent P application in corn growing.

Application Rate
Application rates of P in corn are generally in the range 5 – 15kg/ha, frequently well below the
replacement of 2.9 kgP/tonne of grain or 2.5kg P/tonne of dry weight of silage.

To avoid crop establishment reductions, it is suggested that the maximum rate of seed furrow applied
MAP and DAP should be 4g/m and 2.5g/m respectively (40kg/ha and 25 kg/ha in 100 cm rows). These
rates are for medium clay soils with good planting moisture for a narrow tine opener. For different soils
and soil moisture conditions and where other nutrients are contained in the product an appropriate
adjustment to rates should be made. Seek detailed direction from your fertiliser supplier for more detail.

For deep applied P, the application rate should be sufficient for 3 – 5 years from a single application.

Application Method
The combination of early P requirement for healthy seedling growth and its immobility in soil, means that
fertiliser products need to be applied with, or in close proximity to seed for “starter” response. The target
zone for placement is 5cm to the side of, and 5cm deeper than the seed location.

Where surface and deep soil tests indicated potential for enhanced response from deep application of P
banding around 20cm depth
and at 50cm row spacing early
in a fallow is suggested.

Application Timing
The very low soil mobility
of P in the majority of corn
producing soils requires starter
P to be applied either in the
seed furrow or adjacent (20 –
50mm) to the seed at sowing.

In soils where response to

deep P is likely, timing of
the application should allow
for reconsolidation of the
seedbed by moisture i.e. at the
start or a fallow when there is
soil moisture to 20 – 30cm depth. P deficient corn.

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 POTASSIUM
Potassium is involved in a multitude of functions in the plant ranging from carbohydrate metabolism,
break down and translocation of starches, water-regulation, is essential to protein synthesis formation,
activates enzymes and controls their reaction rates. Adequate supply also improves temperature
hardiness and increases disease resistance.

Corn crops suffering a shortage of K display symptoms such as:

• Interveinal or marginal chlorosis of older leaves;

• Dark green plants with chlorosis along the leaf margins developing to brown striping and necrosis;
• Shortening of internodes and dwarfing plants; and
• Smaller heads and low grain number.

Due to a gradual decline in soil K levels with crop removal, erosion of topsoils, and historically low K
fertiliser application rates, there are an increasing number of soils now requiring K fertiliser applications.
These include red soils (Ferrosols), open downs soils of the Central Highlands, Queensland, other
upland vertosols that developed in situ, and low cation exchange capacity (CEC) acidic coastal soils.
Rain grown summer and winter cereals are less likely to respond to K applications than pulses such as
soybeans, navy beans and peanuts under conditions of marginal soil K status. Chickpea has recently
been identified as sensitive to low soil K. Being more widely grown in rotations with corn, chickpea is
now a key indicator of failing soil K supply.

K deficiency in corn.

CORN HYBRIDS

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POTASSIUM FERTILISER STRATEGIES
Nutrient Source
Potassium is generally applied as either muriate of potash (KCl) or potassium sulphate (K2SO4).
Potassium is also in reasonable concentrations in many manures and composts. Muriate of potash is
generally applied in broadcast or preplant banded applications while potassium sulphate is generally
preferred in blends with P placed in or near the seed furrow.

For deep application the addition of P to the K band can enhance K uptake. Potassium fertilisers are
generally not subject to losses when applied well ahead of crop establishment. Erosion of topsoil and
leaching in acidic low CEC are most likely loss process other than removal in harvested produce.

Application Rate
The vast majority of corn growing soils have adequate to good supplies of K both in the surface and
subsurface. Where applied, application rates of K in corn should be around replacement rates of
3.3kg K/tonne of grain or 10kg/tonne DM in silage.

Most K fertilisers have a high salt index increasing the risk of fertiliser interfering with crop establishment.
As a general precaution K should be avoided in seed furrow placed blends and where unavoidable rates
should be less than 0.25g K / linear metre of row (5kg K/ha in 100 cm rows).

Application Method
Potassium is generally not subject to soil reactions that reduce its long term availability, but is of low
mobility in moderate to high CEC soils. As with P, responses to K in rain grown crops appear to be more
consistent where K is banded in the 15 -25 cm soil layer in combination with and ammonium phosphate
product. Unlike P, K does not stimulate root proliferation response in fertiliser bands. High efficiency of
K use will result from enrichment of a high volume of soil.

Application Timing
In rain grown crops application of K should be complete at crop establishment. There are prospects
of sidedressing response in the 1 – 4 leaf stages in irrigated crops provided it is followed closely by an
irrigation.

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 SULPHUR
Sulphur in the plant is linked to N in a number of biochemical functions. It is an integral part of amino
acids, helps develop enzymes and vitamins and is necessary in chlorophyll formation (though it isn’t one
of the constituents).

Sulphur deficiency in corn is not common in corn growing areas but has been recorded in a range of
shallower upland soils without a gypsum (calcium sulfate) layer in the subsoil. In deeper soils following
periods of flooding, leaching of S increases the probability of low S availability. The practice of double
cropping also increased the chance of S deficiency in above circumstances.

In the initial stages of S deficiency symptoms are often confused with those caused by N deficiency.

Close observation of S deficient plants reveals:

• Commonly occurs as patches in paddock rather than evenly across and area;
• Older leaves are greener than the younger ones; and
• Plants with severe S deficiency. The upper leaves are yellow to white colouration sometimes with
pink colouration toward the proximal end.

S deficiency in corn. Source: IPNI crop nutrient deficiency image

collection.

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SULPHUR FERTILISER STRATEGIES
Nutrient Source
Sulphur is frequently associated with other major nutrients such as N, P, K and Ca in fertiliser products
in the plant-available sulphate form. Elemental S with a micro-fine particle size can be a useful source
of maintenance S but should not be relied upon to correct responsive soils in the short term.

Application Rate
Products containing sulphate-S should be applied at removal rates (1.3kg S/t). Capital rates of S using
gypsum (CaSO4) are frequently at rates 300 – 1000kg/ha (45 -150kg S/ha) being based on attaining
even application and cost effectiveness.

Application Method
Sulphate is mobile in soil water thereby providing a wide range of application options. Options are
generally limited by the other major nutrient in the fertiliser compound. Water running in irrigated
crops is not recommended.

Application Timing
Sulphur requirement in the plant is parallel to N so the range of application timing options are the same
as for N.

16
 ZINC
Zinc aids biochemical processes in plant growth hormones and enzyme systems, is necessary for
chlorophyll production, carbohydrate formation and starch formation.

Although required in relatively very small amounts, Zn is essential during the development of the young
corn plant. Soil tests give some indications as to soil Zn status but requirement is best determine from
visual symptoms, test strips and/or leaf analysis. Similar to P, Zn uptake is affected by a range of soil
and climatic factors. The effect of fallow length and the crop sequence on VAM being very important.
Long clean fallows and corn following canola greatly increase the risk of Zn deficiency. Other factors
that increase chances of Zn deficiency include cool soil temperature at planting, alkaline soils and high
soil availability of P. Effective early Zn nutrition can require multiple application strategies in a single
crop in some soils and seasons.

Symptoms of zinc deficiency include:

• Stunting due to reduction in internode length; and

• White to yellow bands either side of the mid-rib near the base of youngest leaves.

Zinc deficiency in corn. Source: IPNI Crop Nutrient Deficiency Image Collection.

CORN HYBRIDS

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ZINC FERTILISER STRATEGIES

Nutrient Source
Zinc availability from soil applied fertilisers is generally related to water solubility. High water solubility
(sulphates and chelates) ensures availability to plant roots early in the season when they are most
vulnerable to poor soil supply.

Low solubility products such as oxides with small particle size can be effective in some applications.

Application Rate
Zinc is generally applied at rates 5 to 20 times that of removal. Lower rates are generally associated with
foliar applications while higher rates are related to soil application. Many soils show the build-up of Zn
that results from regular use of Zn fertiliser at rate greater than removal.

Application Method
There are a wide range of effective application methods for Zn. They include:

• Broadcast and incorporate capital rates (5 – 10kg Zn/ha);

• Water inject into seed furrow (100 - 800g Zn/ha);
• Seed coating (0.5 - 1.5g/kg seed);
• Banded in blended, coated and compounded starter P products (0.2 – 2kg Zn/ha); and
• Foliar spray (50 - 400g Zn/ha).

Application Timing
Zinc is generally applied when the crop is small. This is to ensure adequacy as the crop reaches the
critical cob formation around the 6 leaf stage. Correction of deficiencies up to tasselling generally
improves yield but yield increase may not match that available from earlier applications (V2 – V4).

COMMENT: EFFECTIVE USE OF

RECYCLED BIO-SOLIDS

In many corn growing areas there is increasing use of recycled bio-solids as nutrient sources.
Although these products are generally highly variable in nutrient analysis they can be very economical
and effective. Availability of nutrients is related to the amount incorporation in organic forms and the
degree of composting. Of the major nutrients the availability of P and K is generally give as 70 – 90%
of regular products whereas N and S is in the order of 20 – 40% in the year of application. Higher N
availability is associated with fresh poultry manure and effluent sludges provided they are incorporated
soon after application.

Although P and K availability from bio-solids is high, access by crop to broadcast requires incorporation
into the soil making it more popular in irrigated crops.

The application rate of these products should always be with consideration of the total P applied as it is
the nutrient with to lowest removal rate with environmental pollution risk where it accumulates in soil.

18
 REFERENCES
Bryson GM, Mills HA, Sasserville DN, Benton Jones Jr. J and Barker AV. 2014. Plant Analysis Handbook
III. Micro-Macro Publishing. Athens Georgia, USA.

Colless JM, 1992. Corn growing, Agfact P3.3.3, second edition. NSW Department of Agriculture, Orange.

IPNI Crop Nutrient Deficiency Image Collection 2012 available at http://www.ipni.net/article/IPNI-3231.

Reuter DJ and Robinson JB. 1997. Plant Tissue – an interpretation manual. CSIRO Publishing.

Steele KW, Cooper, DM and Dyson CB. 1982. Estimating nitrogen fertiliser requirements in corn grain
production. 2. Estimates based on ear leaf and grain nitrogen concentration. NZ Journal of Agricultural
Research, 25, 207-210.

Wortmann CS, Tarkalson DD Shapiro CA, Dobermann AR, Ferguson RB, Hergert GW, and Walters D.
2011. High Yield Corn Production Can Result in High Nitrogen Use Efficiency. Better Crops, Vol. 95, No.
4, p 15.

Zull A, Bell M, Howard H, Gentry J, Klepper K, Dowling C. 2015. A calculator to assess the economics
of deep placement P over time. See more at: https://grdc.com.au/Research-and-Development/GRDC-
Update-Papers/2015/03/A-calculator-to-assess-the-economics-of-deep-placement-P-over-time#sthash.
jsLO3KMc.dpuf

CORN HYBRIDS

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NOTES
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