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Agronomy notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00086
 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: March 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.
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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: UF00066352:00086


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Vol. 31:3 March 2007

April 12 Winter annual forage/wildlife food plot field day- N. FL REC, Live Oak, FL
May 1 Twilight field day N. FL REC, Live Oak, FL
May 2-4 Florida beef cattle short course, Gainesville, FL
May 25 75th Anniversary and field day, Brooksville REC, Brooksville, FL
May 30-June 1 Southern pasture & forage crop improvement conference, Tallahassee, FL
June 5 Beef forage field day N. FL REC, Marianna, FL
June 25-27 Southern conservation tillage conference N. FL REC, Quincy, FL


Fertilization of Bahiagrass Pastures....................................... .......................... 2
Agrotain Fertilizer Additive Potential for Pasture Fertilization ......................2

Frost and Tropical Soda Apple .................................. ........................ 2
Journey Herbicide for Bermudagrass Hay Fields ............................. ............... 3

29th Annual Southern Conservation Tillage Conference.....................................
G et Seed for Crops Early ................. ...................... ..... .......................... 3
Kill Cover Crops Early in Conservation Tillage Plantings.............................. 4
Lim e and Calcium M aterials..................................................... ............... 4
Soil Com action and R oot R restriction ........................................ .......................4
Use Good Rotations ................................................................. ...... 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.

Fertilization of Bahiagrass Pastures

Usually in March we get consistent night time
temperatures that are above 60 F--meaning it is
time to fertilize because active growth will start
on your perennial warm-season forages.
Fertilize with a complete fertilizer in March if
results from your soil test call for the use of a
complete fertilizer. A complete fertilizer has all
three nutrients: nitrogen, phosphorus and
potassium, also known as N P K. If trying to
deliver, for example, 60 lbs N, 15 lbs P205, and
30 lbs of K20, do not use a 10-10-10 fertilizer
blend, but use blends like 20-5-10 at 300 lbs per
acre. How many bags of fertilizer do you need?
- That would be six (6), 50-lb bags per acre if
using the 20-5-10 blend, or seven (7), 50-lb bags
per acre if using a blend with lower N such as
the 16-4-8 formulation.

If the soil tests says phosphorus and potassium
are NOT needed then DON'T add them. If
using ammonium nitrate apply four (4) 50-lb
bags per acre; this rate will provide you with
approximately 65 pounds of N per acre. Could
you apply more? Yes, but this is likely the
most efficient rate. Wait and apply another 50
to 60 pounds of N in mid June July if you
desire to keep the protein level of the grass, hay,

Remember, monitor the weather and apply your
fertilizer whenever you have consistent night
time temperatures above 60 F, and do so prior
to a rainfall event; it will be incorporated into
the soil and uptake by the plant will be more
efficient. Volatilization losses increase when
applying fertilizer after the rain.

Yoana Newman

Agrotain Fertilizer Additive Potential for
Pasture Fertilization

Agrotain is a new product being launched in
Florida and preliminary contacts have been
initiated at University of Florida to examine the
product. This product is intended to treat urea
not the soil-to retard the volatilization or loss
of nitrogen through breakdown of urea in
pasture or hay field situations where fertilizer
will be broadcast.

Due to the increasing problems with the
handling of ammonium nitrate (storage and
transport), use of this fertilizer has become
problematic. Alternatives like urea in pasture
fertilization would become more popular in
Florida if volatilization is reduced.

The product is a fertilizer additive to be blended
with urea fertilizers and urea containing
solutions, like UAN (solution of urea and
ammonium nitrate in water). It is an inhibitor of
urease, the enzyme that breaks down urea, but it
is not a nitrification inhibitor. Therefore, the
amount of time for full hydrolysis (break down)
of urea could be extended to 14 days. The target
of this additive is to minimize the problem of
nitrogen volatilization-associated with the use
of urea, particularly in soils conditions of high
moisture and high temperatures. While the
product is new to the area and no data has been
obtained in Florida, this additive has been used
for several years in the mid south where soils
with high pH offer a high potential for
volatilization of urea.

There are several uncertainties for our
conditions: Most Florida soils are mainly acidic
with some exceptions where pH is 8-8.5.
Therefore, the proved benefits observed in other
locations (higher crude protein of the forage, and
higher forage yields) may not be the same in
Florida, and there are always the added costs
that need to be penciled in.

Yoana Newman

Frost and Tropical Soda Apple

Many people have been asking, "Does Frost Kill
Tropical Soda Apple?" While it may kill
tropical soda apple (TSA) seedlings, the
majority of the plants have well-established root
systems. Therefore, even if the frost is "heavy"
it is unlikely that the root system will be killed.
This means that the plant will come back from
the root system. However, for the time being, it
is going to appear that the plants have been
"controlled." If you remember back to the old
days when Remedy was the only option for TSA
control, it was recommended that TSA plants be
mowed 8 weeks before Remedy application. In
North Florida, frost could substitute as a

mowing operation. In any case, you will need to
apply a herbicide when plants are actively

Why wait until plants are actively growing?
First, we need to understand what happens to
plant cells when they are frozen. Plant cells
contain not only water, but also many other
substances like proteins, amino acids, sugars,
and other solutes that actually lower the freezing
temperature and protect the cells against ice
formation (similar to antifreeze in car radiators).
Although pure water freezes at 32 F, a plant
cell may need temperatures down to 26 F or
lower before the cells will freeze and damage
occurs. Different parts of the plant, different
stages of development of the plant, and different
types of plants can have varying levels of these
"antifreeze" compounds that result in a range of
susceptibility to frost. Environmental conditions
such as drought, cold temperatures, heat, etc.,
can also influence the levels of these
compounds, and thus affect the tolerance to
freezing temperatures. Typically, when a plant
is exposed to a stress factor, including frost, the
plant becomes more hardened, which not only
increases the tolerance to future frost events, but
also increases the tolerance of the plant to

How does frost influence the plant cell? Frost is
basically a water crystal. We all know that
water expands when frozen. The same holds
true inside the plant cell. When the water inside
a plant cell freezes, it expands and upon thawing
the cell is destroyed. Destruction of plant cells
interferes with many things in the plant, but
especially cell to cell transport of nutrients,
water, etc. Essentially, the internal vascular
system is disrupted. This is why an herbicide
application soon after a frost event does not
work as well as applications onto actively
growing, stress-free plants.

The best thing to do if you have TSA and they
have been damaged by frost is to wait until
plants are actively growing. If you need
assistance with the most up to date control
options for TSA, please contact your county

Brent A. Sellers

Journey Herbicide for Bermudagrass Hay

Control of crabgrass, sandspur, and nutsedge is a
common need in bermudagrass hay fields.
Controlling a grass weed in a grass crop can be
very difficult and few herbicides have been
developed for this purpose. However, Journey
herbicide is one option that may prove beneficial
in the future.

Journey is a mixture of imazapic (the active
ingredient in Plateau) and a small amount of
glyphosate. This herbicide combination has
proved to be highly effective on crabgrass,
crowfootgrass, johnsongrass, vaseygrass,
sandspur, fall panicum, and nutsedge. Although
Journey has been marketed for the last 3 years,
the label restricted applications to 'Coastal'
bermudagrass only. However, a supplemental
label was recently released that allows
applications to all bermudagrass cultivars.
It must be noted that Journey, applied over-the-
top of bermudagrass, will result in temporary
yellowing and stunting. This injury will be
made worse if the application is made during
spring transition or during prolonged periods of
dry weather. Therefore, it is important to only
use Journey on bermudagrass that is actively
growing. When applied during active growth,
expect 2 to 4 weeks of stunting followed by
rapid recovery.

Jason Ferrell

29th Annual Southern Conservation Tillage

The SCTC will be held at the NFREC in
Quincy, FL on June 25-27, 2007. The posters
and presentations will be made on the 26th at
NFREC in Quincy and the field tour will be on
the morning of the 27th of June at NFREC in
Marianna. The theme of the program this year
will be "Sod based rotations- the next step after
conservation tillage".

David Wright

Get Seed for Crops Early

The varieties of peanut and corn that you want to
plant may be in short supply this year. Cotton
and soybean varieties should be adequate. With

the increase in corn acreage that is expected, the
best hybrids will be in short supply. Peanut
varieties will also be in short supply for several
new ones that have performed well in variety
trials. It will take 2-3 years before these peanut
varieties will be in large enough supply to plant
large acreages. Check variety reports for next
best options and change in management needed
to grow most economic yields.

David Wright

Kill Cover Crops Early in Conservation
Tillage Plantings

Cover crops need to be killed 4 to 5 weeks
before planting cotton or peanut. This reduces
the chance of drying out the soil; also, most of
the soil insects die before the new crop is
planted reducing the chance of stand loss due to
insects. Dry and brittle cover crops make it
easier to plant into since they seldom drag on the
strip till rig as a wilted cover crop might. It is
very difficult to have a large cover when
planting corn early but cover crops can be very
large by early April when most of them need to
be killed for both cotton and peanut. Soybeans
are often planted after wheat or other small grain
which desiccate during the dry down process of
the grain so that soil insects are not usually a
problem for a crop planted after small grain

David Wright

Lime and Calcium Materials

Limestone (calcium carbonate) and Gypsum
(CaSO4) are both excellent sources of calcium
for crop production. The difference between
these materials is that limestone also neutralizes
acidity while gypsum does not change soil pH.
Florida soils are naturally acidic and thus require
periodic liming to adjust soil pH for optimum
crop production. A ton of calcium carbonate
limestone applied to correct soil pH, means that
800 lb/A of Ca is being applied. Even a
dolomitic limestone will contain over 400 lb
Ca/ton. Crop removal of calcium ranges from 5
lb Ca/A for corn grain to 30 lb Ca/A for a high
yielding silage crop. Legume crops may require
a higher pH for optimum rhizobium activity.
Thus regular liming to maintain soil pH in the
optimum range will easily maintain calcium

levels against crop removal. Peanuts are one of
the higher users of Ca and if crops are grown in
rotation with peanuts, lime and gypsum applied
on peanuts every 3-4 years is probably adequate
for the other crops grown in rotation. Gypsum is
sometimes used as a Ca fertilizer for crops
where Ca is needed but a low pH is desired for
optimum growth of the crop making lime a poor
choice for meeting this need. Gypsum is often
discussed as being related to improving soil
physical properties. Adequate Ca and Mg are
important for promoting and maintaining good
soil aggregation. However, if soils have
adequate K and Mg and are limed to an optimum
pH there will be plenty of these cations to
maintain good soil structure and no further
adjustments are necessary. Soil testing and
regular liming are the keys to healthy crop
growth and good soil structure.

David Wright

Soil Compaction and Root Restriction

The first step in minimizing soil compaction is
to avoid field operations when soil moisture is at
or near field capacity. Always let the field dry
before doing field work. There are several
management decisions that can be made to
reduce soil compaction including: 1) A quick
field test conducted by molding soil between
your index finger and thumb and observing the
stability of the resulting soil ribbon, or molding
soil into a ball in your hand and observing
whether the soil breaks apart when you touch the
ball. If the soil smears much like grease, it is too
wet and soil should be allowed to dry some
before traffic is allowed over the fields. 2) The
use of controlled traffic lanes where possible.
Farm equipment is getting larger and heavier
and results in more soil compaction. 3) Check
wheel and tire size and pressure. Larger wheels
and tires allow better flotation, whereas lower
tire pressures reduce the load on the soil.
Increase the tire's "footprint" with larger wheel
diameters. 4) Consider applying lime and other
operations in the fall on drier soils. 5) Consider
conservation tillage. Conservation tillage is the
best long-term solution. It avoids tillage and
passes through the field and does not disrupt the
soil structure as much. There are often roots that
hold the soil together and allow heavier
equipment without causing severe soil
compaction. In most cases growers use in-row

rippers to break the natural compaction layer
observed in most Coastal Plain soils. This will
eliminate soil compaction for that crop and often
leads to increased yields due to deeper rooting

David Wright

Use Good Rotations

This year is a good year to rotate to other crops
if good rotation has been lacking. Good prices
for corn, soybeans and wheat may allow growers
options that have not been available for an
economic return during the past few years.
Consider crops with the lowest amount of risks

and highest potential return. Corn makes an
excellent rotation for peanut, cotton, and
soybean and price is almost double over the past
several years. Corn responds to irrigation more
than almost any crop so adequate water should
be available to grow the crop profitably.
Soybeans may fit with other growers who have
grown cotton for a number of years. Well
rotated land can lead to soybeans yield of 50-60
bu/A with low inputs. Cotton and peanut prices
have been stagnant for a few years but can still
be profitable if high yields are obtained and the
best way to have low input costs and high yield
is through good rotation.

David Wright

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; J.A. Ferrell, Extension Agronomist I 1Ii. I I, .I Y.C. Newman, Extension Forage Specialist
., .,, il..i,, B.A. Sellers, Extension Agronomist .1, I., 1 I, ,,l ..I i D.L. Wright, Extension Agronomist IdlJ a ifa..ufl.edui.