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Agronomy notes
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066352/00088
 Material Information
Title: Agronomy notes
Uniform Title: Agronomy notes (Gainesville, Fl.)
Physical Description: v. : ill. ; 28 cm.
Language: English
Creator: Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Place of Publication: Gainesville
Creation Date: May 2007
Subjects / Keywords: Crops and soils -- Florida   ( lcsh )
Crop yields -- Florida   ( lcsh )
Agriculture -- Florida   ( lcsh )
Agronomy -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
periodical   ( marcgt )
serial   ( sobekcm )
Statement of Responsibility: Florida Cooperative Extension Service, University of Florida, Institute of Food and Agricultural Sciences.
General Note: Description based on: January 1971; title from caption.
 Record Information
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000956365
notis - AER9014
System ID: UF00066352:00088


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May 2007


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M icronutrient D eficiencies in Corn ........................................ ...... ............... 2
N itrogen Fertilization of Corn ........................................... .......................... 2
Planting Decisions ................... .. ........... ... ............ .. ............. .. 3

Cotton Planting Investment.................................................................. ..............3
Seed Treatment Chemicals for Nematode Management in Cotton .....................4

Aeschynomene and Alyceclover Two Good Summer Legume Option.............4

Economics of Peanut Rotation with Bahiagrass....................................................5

The Importance of Sprayer Cleanout after Valor .........................................5
Questions of Pesticides? ........................ ...... .. ..... .............. ..6

Vol. 31:5

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity _Affirmative Action Employer authorized to
provide research, educational information and other services only to individuals and institutions that function without regard to race, color,
sex, age, handicap or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension
Office. Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Larry Arrington, Dean.

Micronutrient Deficiencies in Corn

As corn acreage expands more nutrient
problems will be observed. Most of the corn
grown in Florida over the past several years
has been around dairy farms. Many of the
fields may get much of the dairy manure
applied back on the fields. These fields may
increase in pH as more manure is applied
resulting in more micronutrient deficiencies.
Likewise, peanut acreage has expanded
outside the traditional peanut area over the
past few years. Where peanuts are grown,
high levels of Ca, as lime, are often applied
resulting in higher pH levels. Manganese
deficiencies are observed most often on well
drained, sandy soils with a high pH. The
entire corn plant may have a yellow cast to
it. This often occurs if the soil pH is above
6.5. If soils are known to be deficient in
Mn, Mn should be applied in the starter
fertilizer near the row. The starter may
often be slightly acidic which allows Mn to
be available for a longer period of time
without being tied up; a way of correcting
the Mn deficiency in the most effective
mode. Manganese sulfate is the most
common carrier of Mn and is effective if a
deficiency is noted early and foliar
applications can be made. However,
Manganese sulfate does not mix well with
many starter fertilizers so chelates are often
used at low rates. These are not usually as
effective as sulfate forms. It has been
shown that 5 lbs of Mn material applied in a
band is as effective as 10 times that amount
applied broadcast due to Mn being tied up
rapidly as it is exposed to the soil. Several
people have found the effectiveness of
MnSO4 > MnO. Zinc is also a
micronutrient that can be deficient in corn
on sandy, high pH soils. However, if corn is
rotated with peanuts, use as low rates as
possible to prevent toxicities in peanuts.
Again sulfate forms of Zn are probably the
most effective followed by the oxide form.
Chelates vary in their effectiveness and
some may be as effective as the sulfate form
while others will be less effective. The total

amount of micronutrients delivered in
chelates is low (usually around 5%)
compared to sulfate or oxide forms which
vary from 26-78% depending on the source
for Zn and Mn. Applying micronutrients as
a corrective measure during the growing
season should be done as soon as the
deficiency is identified. Our research
indicates that if the application is made too
late no yield advantage will be found
compared to applying early in the season.
Zinc and Mn are the two micronutrients
most often deficient in corn. Boron is
another micronutrient that we routinely
recommend for corn since it is mobile and
can be leached out easily. We have not had
yield responses on corn to Cu and Fe in any
of our trials; however, there may be soils
that are deficient in these nutrients too.

David Wright

Nitrogen Fertilization of Corn

Nitrogen is the nutrient that requires the
highest level of management on corn. It is
more mobile than the other macro elements
and has a higher total uptake than all
nutrients except potassium which is similar
in total uptake. There are several ways to
utilize N more efficiently and in most cases
rates as low as 180-200 lbs/A would
produce the highest yields under irrigated
conditions. These practices include:

-Split applications, with N going out
just prior to plant needs. This
practice guarantees that N will not be
leached or volatilized and will be
available when the plant needs it.

Application of N near the row at
plant and doing it on the first
sidedress application or as late as
equipment can be used for

-Use of conservation tillage planting
methods since moisture conditions

on the crops are often better due to
higher OM and soil cover which
results in better nutrient use

Application of N to corn all at
beginning of the silk-tassel period
since nitrogen is especially important
during the vegetative stage of corn
production. Grain protein content is
increased mainly with later
applications with little or no increase
in yield.

Most of the weight gain of a corn crop is due
to grain after silk/tassel with little vegetative

David Wright

Planting Decisions

Most growers have figured out what they
will plant by this time of year but there have
been reports of growers killing out small
grain to plant corn due to the high price.
Corn prices were not this high when many
people decided to plant small grain in the
fall. And corn prices are double compared
to the average price for the last 10 years and
may go as high as $5/bu according to some
reports. The decision to kill out a small
grain crop that has already had quite a bit of
management in it should be made with care
since many of the best corn hybrids were in
short supply early in the season and even
poorer choices for growers are out there
now. The wise decision at this point is to go
with what has been planned and look at crop
prices in the fall to determine the best
choices for your farm. This spring has not
been good for dryland corn even though it
has not been hurt too badly due to the low
water requirements up to now. However,
corn will continue to need more water as the
corn nears the ear fill period and then will
reach peak water use during this ear fill
period. Most of the crop prices have been
pulled up by corn prices which will probably

continue to influence those markets. For
those who decided to plant corn, it is a good
rotation crop with cotton and peanuts as well
as soybeans and will have an impact on the
yield of those other crops.

David Wright

Cotton Planting Investment

The Deep South has been particularly dry
during the spring of 2007 raising a lot of
concern about getting stands of cotton.
Growers should try to plant cotton if
possible in the April 10- May 15 time
period. This time bracket allows growers to
take advantage of any early rains and also
allows time for replanting if necessary.
During cool, dry years thrips can be
especially damaging to young cotton
seedlings since growth is slow. In-furrow
insecticides usually do a good job of
controlling thrips for 2-3 weeks unless there
is not enough moisture for the plants to take
up the in-furrow insecticide. In some years,
thrips numbers may overwhelm the in-
furrow material. When thrips numbers are
so high, it may take additional few feeding
punctures for the thrips to ingest enough
material to be killed. These high thrips
numbers result in high number of feeding
punctures in the plant which show the
typical plant symptoms of crinkled leaves
and stunted growth. If thrips numbers are
still high after 2-3 weeks, consider foliar
applications of insecticides to aid early
growth so that post directed applications of
herbicides to cotton can be made earlier.
Early post-directed applications are
becoming more important as we get more
weed resistance to herbicides from hard to
control weeds like pigweed and tropical
spiderwort. Likewise, most of our cotton
acreage is now planted under conservation
tillage practices and in-furrow insecticides
will also help reduce problems from other
soil insects. Cover crops are often killed too
close to planting time and soil insects are
still feeding on the roots of the cover crop

when cotton is planted. As soon as the
young cotton seed germinates, soil insects
see a new food source and will begin
feeding on roots and the stem of the
developing plant. Hence, we recommend
that cover crops be killed 4-5 weeks prior to
planting to allow time for the plants to
completely dry out leaving no food for the
soil insects to survive on. Early destruction
of cover crops will reduce the soil insect
population and help reduce problems for the
new seedlings. More and more technology
is being placed on and in the seed of cotton
and cost for seed is more expensive;
therefore, we need to make sure that this
part of the investment is protected with as
good of practices as we know how to use.

David Wright

Seed Treatment Chemicals for Nematode
Management in Cotton

The development and marketing of
nematicidal seed treatments is a relatively
new development, and the products were
targeted initially for use on cotton seed.
Avicta Complete Pak, a product of Syngenta
Coporation, was registered on cotton in
2006 and widely used on the crop that year.
The seed treatment Aeris, from Bayer
Corporation, is registered for use in cotton in
2007. Both products are mixtures of
chemicals that are formulated to provide
early season suppression of nematodes,
thrips, and fungal seed pathogens. Avicta
Complete Pak contains the nematicide
abamectin plus thiamethoxam for thrips and
azoxystrobin plus other fungicides for fungi.
Aeris is a combination of thiodicard for
nematodes and imidacloprid for thrips
control with a fungal seed treatment option
available as well. A number of field trials
have been conducted on cotton with these
products over the past three years in the U.S.
Results for nematode management have
been mixed but generally positive for
deploying these seed treatments as

'supplements' to nematode management
programs in cotton. Field trial results and
subsequent university recommendations for
use of these products vary by cotton
production state due to differences in
nematode species and population densities,
crop rotations, edaphic factors and economic
considerations. Recommendations for
integration of these new products into
existing cotton nematode management
programs in Florida are evolving as more
information is obtained through field trials
and grower experience. Grower acceptance
of these products has been high due to the
ease of handling (no chemicals to apply) and
greater grower use is expected in the future.
It must be clearly noted, however, that these
seed treatments act as only 'early season
nematode suppressants' and must be used in
combination with other nematicides or good
rotations in fields where moderate to high
nematode population levels are present.

Jimmy Rich and David Wright

Aeschynomene and Alyceclover two
good summer legume options.

Aeschynomene and Alyceclover are two
well adapted warm-season legumes that are
grown all throughout Florida. They can be
grown on a prepared seedbed or overseeded
into your warm-season pastures. However,
their adaptation to soil drainage is very
different. Let's look first at Aeschynomene
americana or american jointvetch or
deervetch, as is commonly known.
Aeschynomene is very palatable to cattle
and deer, and adapts wells to flatwood soils
that are poorly drained. It is mainly
recommended for grazing (not
recommended for hay) and the season of
growth goes from April to November. Soil
moisture is critical for this legume, and
seeding rates are 5-7 lbs per acre when using
hulled seed or 10-15 lbs per acre when
seeding with intact seed where the hulls are
still present. Planting of hulled seeds should
be done early; this year planting can be done

as soon as May depending on weather
conditions. If using dehulled seeds, planting
can be done in June. If planting is delayed
past the middle of June, the amount of
grazing time is reduced due to the delayed
development of the Aeschynomene.
Seedlings that emerge after initial rains in
May, may not survive if drought condition
comes back and is longer than 7-10 days
after seedlings emerge. Alyceclover, on the
other hand, is adapted to moist soils that are
well drained. It can be used for grazing and
hay. If used for grazing, do so only if
rotationally grazing because is not as
grazing tolerant as Aeschynomene. When
used as hay, it makes high quality hay;
Alyceclover may be a good option for
dairymen in need of additional forage in late
summer and early fall. The season of
growth for Alyceclover goes from May
through September and seeding rate is 15 lbs
per acre. One issue about Alyceclover, is
that it is susceptible to root nematodes (the
peanut root-knot nematode, and the southern
root-knot nematode). You should expect
some stunting due to nematode damage to
the root if the field that you are planning to
plant has a history of vegetable crops
(particularly those in the cucurbit family like
cucumber, melon, squash, etc) as these crops
attract or build up the nematodes in the soil.

Yoana Newman

Economics of Peanut Rotation with

A five year study comparing peanuts grown
following 2 years of cotton vs. 2 years of
bahiagrass followed by a year of peanuts
then cotton resulted in peanut yields
averaging almost 1250 lbs/A more in the
bahiagrass system. In each of the five years,
peanuts in the bahiagrass rotation without
irrigation out yielded peanuts with irrigation
in the 2 year cotton rotation. When
economics of the system were looked at,
dryland peanuts following bahiagrass were
$175/A more profitable than irrigated

peanuts in the system commonly used by
growers. The best conservation tillage
practices were followed in both systems
reducing costs of both systems. The best
rotations are often not followed due to lack
of experience with the crop, lack of
equipment, markets or other factors;
however, with the cattle and livestock that
exist in Florida and the SE, bahiagrass is a
very viable option and should be considered
by growers. Having cattle can be beneficial
for grazing the row crop land in the winter
after harvest resulting in maximization of
farm resources.

David Wright

The Importance of Sprayer Cleanout
after Valor

Due to the recent increase in Cadre resistant
weeds, more peanut growers than ever are
interested in using Valor preemergence.
Considering that Valor has a different mode-
of-action than Cadre, and that it controls
many broadleaf weeds, it is a natural fit for
fields with a long history of Cadre use.
However, it is important to be aware of the
problems with tank cleanout associated with

Valor has been shown time and time again
to stick in sprayer hoses, fittings, and
screens. Over time, Valor residue will
slowly dislodge and cause crop injury,
particularly when spraying glyphosate.
Since cotton is very sensitive to Valor, it is
important to clean the sprayer very
diligently after each Valor application.

It is critical to clean the sprayer immediately
after Valor is used. Valor should not sit in
the sprayer over night or large amounts of
herbicide will begin to settle in the system.
After Valor has set in the system for an
extended period of time, cleanout is almost
impossible without replacing fittings and
sections of hose. Therefore, after each
Valor application the sprayer should:

1. Be rinsed with clean water and
2. Filled with an adequate amount of
clean water and ammonia (1 gallon
of ammonia per 100 gallons of
water) to be circulated and sprayed
through the system.
3. Rinsed again with clean water.

If these steps are followed, the risk of
having cotton injured with Valor residue
will be greatly reduced or eliminated.

Jason Ferrell

Questions about Pesticides?

Do you, your colleagues, or your clients
have questions about pesticides? Perhaps,
you might be interested in a reputable
pesticide information resource offered by
The National Pesticide Information Center
(NPIC). This center provides a toll-free
telephone service offering objective,
science-based chemical, health, and
environmental information about pesticides.
If you receive questions such as:

Are my pet birds sensitive to
pesticides applied inside my house?
How long should I keep children and
pets off the lawn following a
pesticide application?

What are my management options
for my backyard vegetable garden
that had pesticides drifted onto it?
How long does it take for pesticides
to breakdown in the environment?
Where can I find general information
on pesticides?

The NPIC provides real answers and
everyday questions are answered from the
general public, health care providers,
veterinarians, government agencies, and
others across the U.S. The goal of NPIC is
to provide unbiased information about a
variety of pesticide-related topics, in order
for individuals to make a more informed
decision when using pesticides.

Free brochures are available from NPIC to
provide clients with contact information
regarding pesticides. You may request
quantities (up to 100) of free contact
brochures by calling 1-800-858-7378, or
writing to the National Pesticide Information
Center, Oregon State University,
Environmental and Molecular Toxicology,
333 Weniger Hall, Corvallis, OR 97333-

Fred Fishel

The use of trade names does not constitute a guarantee or warrant of products named and does not signify approval to the exclusion of similar
Prepared by: J.M. Bennett, Chairman III.I, ,11l .1h,, J.A. Ferrell, E M, ...r. ._.....,., 1 I I I ll, ,,1 il .I F.M. Fishel, Pesticide
C(-.l...i. i ii ..I.I. ., ,i I ..I,, Y.C. Newman, Extension Forage Specialist .. ,,ii .ih i Jimmy Rich, Extension Entomology and
Nematology Specialist; D.L. W right, E 1,. 1 .,. ...1..1 1 .1 i i, ,, .I,,1 .