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Agronomy notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00080
 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: November 2000
 Subjects
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 )
 Notes
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: UF00066352:00080

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AGRONOMY

L!, NITVER TTY OF
.: FLORIDA
EXTENSION NOTES Ne r
i..... 11 F.-..- A .u..r..' .l. No m er-December 2000

DATES TO REMEMBER

January 23-24 Agronomic Crop In-Service Training NFREC-Quincy
Southern Agricultural Workers Meeting

January 28-30 Southern Branch Meeting American Society of Agronomy
Ft. Worth, TX

IN THIS ISSUE PAGE

COTTON
M essenger Reduces Hard Lock Cotton ......................................................... ................. 2

PEANUT
P eanut Q u otas ..... ........................................................... ......................... ............... ...... 2
F arm -Sto red P eanu ts ............................................................................ ................................. 2

POISONOUS PLANTS
C astor B ean ............. ..... ........... ............ ........ 2
C coffee W eed ..... ............................................................... ..................... ............. ...... 2
F ro sted S o rghu m s .................................................................................. ................................ 3
G rass T etany in C battle .................................................................................................................. 3

TOBACCO
Selecting a Tobacco Variety for 2001 ............................ .... ......................................... 3
Tobacco Curing Barn Retrofitting ................................................. ................................. 4
Tobacco Farmer Partnering Program by Philip Morris ..................................................... 4
T tobacco Q uota for 200 1 ........................................................... ............................................ 4
Tobacco Plant B ed Fum igation ........................................... .................................................. 4
Fertilization of Tobacco Plant Beds .............................................. ................................. 5
A void Tobacco M osaic V irus ...................................................................................... 5

WEED SCIENCE
N ew Touchdow n Form ulation ............................................. .................................................. 5

GENERAL
Cover Crops for Strip Till Planting ............................................... ................................. 5
Crop R stations ............. ..... ........... ............ ........ 5

P U B L IC A T IO N S ................................................................................ ............................................ 6

N O V EM BER CR O P E STIM A TE S ............................................... .................................................. 6

The Institute of Food and Agricultural Sciences is an equal 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 Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences
/ University of Florida / Christine Taylor Waddill, Director.








Messenger Reduces Hard Lock Cotton


A new plant health material from Eden Biosciences has been
shown to reduce hard lock in cottonby as much as 50% when
applied in 4 applications about 2 weeks apart starting at first
square. This is some of the first data on control of hard lock
in cotton with Messenger. Yield responses with the material
have averaged about 15% over studies conducted during the
last 4 years. Subsequent data from this year should help de-
termine the best time of application for the material.


moles. Horses are most susceptible to poisoning, but all live-
stock and humans can be affected. All parts of the plant are
toxic, especially the seeds. Toxicity is seen most often in
spring and summer."

Control Mowing of very large plants may provide all of the
control that is needed especially in the fall. If only a few
plants are present and if they are carrying seed, removal by
hand will prevent the spreading of seed. In the spring, as seed
germinates and new plants develop, commonly used pasture
herbicides will likely control small plants.


DLW


CGC


Peanut Quotas


The peanut quota for 2001 will be the same as in 2000, ac-
cording to the USDA. The quota is determined by estimates
of the need for domestic edible and related uses in the next
marketing year. The average quota support price is set by
law at $610. The price support for additional peanuts will be
announced by February 15, 2001.


EBW

Farm-Stored Peanuts

Farmers who store peanuts on the farm for seed use or other
purposes should protect and maintain their quality. Moisture
content should be checked periodically and kept below 10
percent. If the peanuts are stored in wagons, heat can be
added as needed, or it may be possible to just run the fans
during low-humidity days to reduce the moisture. Be sure to
turn the fans off at night unless heat is added. If the peanuts
are stored in a building, ventilation should be used to keep
moisture at safe levels. Protect the peanuts from rodents,
squirrels, birds, and other animal pests.


EBW

Castor Bean

Last year, I had a question about castor bean in a pasture. Is
castor bean poisonous? Yes, castor bean is poisonous. Castor
bean is a perennial in the tropics and subtropics, but acts as
an annual in much of the South where frost occurs. "Found
throughout the Southeast; cultivated and occasionally escap-
ing and persisting inpinelands, waste places, and roadsides."
I have seen it growing in South Florida along roadsides and
on mounds of topsoil stockpiled by the highway department.

Toxicity "The poisonous principle is a phytotoxin called
ricin. In the Southeast the plant is commonly planted not
only as an ornamental but also in vegetable gardens to repel


Coffee Weed

A publication SP 57, "Poisonous Plants of the Southeastern
United States" is available from the University of Florida
Institute of Food and Agricultural Sciences for the cost of
$4.00.

Recently, there have been reports of animal deaths from eat-
ing coffee weed. There are two plants commonly called cof-
fee weed that can cause a problem; these are sicklepod (Senna
obtusifolia) and coffee senna (Cassia occidentalis).

The following comes from the older book entitled "Poison-
ous Plants of the Southern United States":

Both plants are summer annuals. Coffee senna is very
similar to sicklepod but has mostly 8 or more leaflets
rather than 4 to 6. The pods on coffee senna are flat-
tened while those of sickle pod are nearly four-sided.
Also, coffee senna pods tend to be straighter and
shorter than those of sicklepod. The end of leaflets of
coffee senna are pointed whereas those of sicklepod
tend to be rounded. These plants are found through-
out the South but are more abundant on sandy soils of
the coastal plain, and are most abundant in cultivated
fields, roadsides, waste places and open pinelands."

Toxicity The toxic principles have not been clearly estab-
lished. The seeds appear to exert their toxicity upon the skel-
etal muscles, kidney, and liver. The leaves and stem also
contain toxin, whether green or dry. Sicklepod is much more
prevalent but somewhat less toxic than coffee senna. Ani-
mals can be poisoned by consuming the plant in the field, in
green chop, in hay or if the seed is mixed in grain. Toxicity
has been observed in cattle. It should be assumed that other
animals are susceptible to the effects of these plants.

Symptoms Diarrhea is usually the first symptom observed.
Later, the animals go off feed, appear lethargic, and tremors
appear in the hind legs, indicating muscle degeneration. As
the muscle degeneration progresses, the urine becomes dark
and coffee-colored and the animal becomes recumbent and








is unable to rise. Death often occurs within 12 hours after
the animal goes down. There is no fever.

Treatment Once animals become recumbent, treatment is
usually ineffective. Selenium and Vitamin E injections have
been used with variable results.


CGC

Frosted Sorghums

Sorghums, sudangrass, andjohnsongrass will produce prus-
sic acid after a frost or freeze. The frosted forage will pro-
duce large quantities of prussic acid when the plant cells break
down in the cow's rumen. This may cause prussic acid (HCN)
poisoning.

If the forage is allowed to dry for 3 to 6 days it should be safe
to consume. As the plants dry, the toxic compound will be
released to the atmosphere as a gas. In the fall remove ani-
mals from these pastures when frost is eminent. [Pearl millet
does not produce prussic acid.]

Also do not allow animals to graze young regrowth (south
Florida) that may appear after the tops have been killed by a
frost. At any time during the growing season, always allow
these plants to reach a height of 18 to 24 inches before graz-
ing since the young plants have a higher concentration of
prussic acid, frost or no frost, and can be dangerous.

Frosted sorghums canbe harvested for silage. The danger of
prussic acid poisoning is minimized since the forage is
chopped coming out of the field and then handled again when
taken out of the silo. This provides ample opportunity for
the toxin to escape to the atmosphere. Alight frost may even
be helpful if sorghum is harvested for silage since it will al-
low the plant to dry down. The forage sorghums often con-
tain too high a level of moisture when harvested direct (with-
out wilting) for silage.

Sorghums and other warm season annual grasses that have
received moderate to high rates of nitrogen fertilizer and have
been under drought stress may contain toxic levels of nitrates.
If levels are high enough, nitrate poisoning can occur. Dry-
ing or harvesting the plants for silage does get rid of the ni-
trate. In some situations, the potential for nitrate poisoning
may be greater than for prussic acid poisoning.


CGC

Grass Tetany in Cattle

Grass tetany, sometimes called grass staggers or hypo-
magnesemia, can be a serious problem in Florida with cattle


grazing small grain or ryegrass pastures. The problem is usu-
ally confined to lactating cows. The exact cause of the dis-
ease is unknown, although it is always associated with an
imbalance in the mineral components of blood serum, espe-
cially reduced magnesium levels. In Florida, the disease is
more severe when cattle are grazing young forage, particu-
larly the first flush of growth during December and January.
Once the forage becomes more mature, the likelihood of prob-
lems occurring is reduced. The disease is apt to appear un-
der conditions of nutritional stress. Placing cattle on winter
pasture directly after being on frosted or other low quality
pasture may cause such a nutritional stress.

The symptoms of hypomagnesemia closely resemble those
of milk fever or ketosis. These include nervousness, lack of
coordination, muscular spasms, staggering, and death. When
the disease is suspected, a veterinarian should be called im-
mediately to diagnose and to initiate treatment. However, in
beef herds, the herdsman does not always have the opportu-
nity to observe the signs of the disease and affected cattle
may be found dead in the pasture.

Factors which have been associated with this disease include
low levels of magnesium (Mg) and high protein and potas-
sium levels in the forage. Use dolomitic limestone, which
contains magnesium, to increase forage magnesium levels if
the level of soil magnesium is low. On soils with a high pH
level, magnesium can be included with fertilizer materials.
Excess nitrogen in conjunction with high levels of potassium
fertilization tends to reduce the magnesium level in most for-
age plants. Consequently, these fertilizer elements should
not be applied in excess on temporary winter pastures. Fol-
low recommendations based on soil test results.

Grass tetany can be prevented by feeding mineral supple-
ments that contain magnesium. Commercial mineral mix-
tures containing 10-15% magnesium are available for feed-
ing during periods of increased grass tetany probability. Cattle
need to consume 6-12 ounces/head/day of this mineral. (For
additional information on this problem, see the publication
Agronomy Facts SS-AGR-64 "Grass Tetany in Cattle").


CGC


Selecting a Tobacco Variety for 2001

Generally Florida tobacco farmers prefer varieties that, in
addition to producing good yields and quality, have resis-
tance to root-knot nematodes and "hold well" in the field.
Most often a variety that "holds well" has nematode resis-
tance and is tolerant of the brown spot disease. The K 326
variety has been the most popular variety in Florida for these
reasons, and will probably remain the leading variety in 2001.
However, K 326 does not have much resistance to black shank,








so farmers with severe infestations of this disease may have
to make other variety selections. NC 71, NC 72, K 346,
Speight 168, Speight 172, and othervarieties have highblack
shank resistance as well as nematode resistance and other-
wise produce well in Florida. For those farmers who consis-
tently have losses to potato virus-Y and tobacco etch virus,
but no black shank, NC 55 would be a good selection. It is
the only variety with such resistance. There was consider-
able tobacco mosaic virus (TMV) in other states in 2000,
which may create interest in a TMV-resistant variety NC
297 has resistance to TMV and also has high black shank
resistance. Quality of NC 297 may not be outstanding, based
on limited testing in Florida, but it is probably better than
other TMV-resistant varieties. Some growers may wish to
grow a non-flowering variety because of the ease of sucker
control. Speight NF3 and OX 414NF have performed well
in Florida. If a grower does not retrofit enough barns to eas-
ily cure his entire crop, he may want to select an early-matur-
ing variety, such as Coker 371-Gold or K 394 for part of his
acreage, thereby enabling him to extend his harvest season.


EBW

Tobacco Curing Barn Retrofitting

One of the first questions a grower may have about retrofit-
ting is how many barns to retrofit. Naturally the answer is to
retrofit as many barns as needed to cure the 2001 crop. The
quota will be announced on December 15, so the grower then
only needs to divide his quota by the number of pounds he
can cure in one barn in one season and he will have the an-
swer. It is important not to assume that because Stabilization
provides a total of 13 cents per pound of 2000 quota and
$2600 per barn that this all he should retrofit. This rate of 13
cents per pound and $2600 per barn calculates out to 20,000
pounds of tobacco cured in one barn for the season. Few
farmers can cure 20,000 pounds per barn per season, and
therefore may have to retrofit more barns than the payments
would cover at the above rates. If the 2001 quota is the same
as in 2000, enough barns should be retrofitted so that the
grower will not be tempted to use non-retrofitted barns if he
is unable to cure tobacco as fast as it matures.


EBW

Tobacco Farmer Partnering Program
by Philip Morris

Philip Morris has announced that they plan to expand their
Tobacco Farmer Partnering Program into the flue-cured states
in 2001. This program was started in the burley area in 2000
and involves the contracting of tobacco. Details will be pro-
vided in January 2001. In the burley areas, farmers who con-
tracted with Philip Morris delivered their tobacco to desig-


nated locations. It is expected that the Philip Morris con-
tracts will be similar to contracts offered by other compa-
nies, in that they will be primarily marketing contracts rather
than production contracts. Production contracts usually in-
clude specifications on how the commodity is produced, as
is the case in many of the poultry contracts. Marketing con-
tracts may involve quality requirements that are affected by
production practices, but decisions on variety, fertilization,
pest control, and management are usually left to the grower.
Grading standards, pricing, and other details such as the
method of selecting participating growers should be an-
nounced in January.


EBW

Tobacco Quota for 2001

The USDA has announced that the 2001 flue-cured tobacco
basic quota will be 548.9 million pounds, an increase of about
one percent from the 2000 quota. The quota is determined
by a formula that included 297 million pounds of purchase
intentions by the domestic cigarette manufacturers, a 3-year
average export level of 297.7 million pounds, a reserve stock
adjustment of minus 61.8 million pounds, and the USDA
secretary's discretionary adjustment of plus 16 million pounds.
The effective quota for 2001 will be about 543 million pounds,
which reflects over-marketings of the 2000 crop. The aver-
age support price will be $1.66 per pound, which is up 2
cents from 2000. The no-net-cost assessment will be 5 cents
per pound, with half paid by the producer and the other half
paid by the purchaser.


EBW

Tobacco Plant Bed Fumigation

Prior to fumigation, plant bed soils should be well-prepared
so that the fumigant penetrates the top few inches. Break up
clods and trash that could protect weed seed and disease
organisms from the fumigant. If the soil is dry, irrigate a few
days before fumigation to help soften the seed coats of weed
seed to increase the probability of their control. Fumigate
when the air temperatures are above 55 degrees. Fumigants
for tobacco plant beds will likely contain 20-33 percent chlo-
ropicrin this year. It should be remembered that chloropicrin
does not dissipate from the soil as quickly as methyl bro-
mide. To avoid the possibility of damage to tobacco seed,
the aeration period, or the interval between removing the plas-
tic film and seeding of the tobacco, should be extended up to
two weeks to insure that chloropicrin is no longer at toxic
levels in the soil. Poor stands of tobacco could result from
the residual chloropicrin.

EBW









Fertilization of Tobacco Plant Beds


Avoid excessive fertilization of tobacco plant beds prior to
seeding. If fertilizer salts are excessive, germination and
stands can be reduced, especially when rainfall is low. Re-
member that a rate of 50 pounds of fertilizer per 100 square
yards of bed area is equivalent to over a ton per acre. Use a
fertilizer that has most, if not all, of the nitrogen in the nitrate
form. Irrigate well after seeding, and then as needed to keep
the bed surface moist. Adequate moisture helps reduce fer-
tilizer injury, but do not water excessively as diseases such
as blue mold and damping-off can become more severe. If
additional nutrients are needed they can be top-dressed over
the beds.

EBW


Avoid Tobacco Mosaic Virus


Tobacco mosaic virus (TMV) became a problem in many
areas in 2000. The probability of TMV becoming a problem
can be reduced by following good sanitation practices. Do
not use tobacco products when handling tobacco plants be-
cause the virus can survive in some tobacco products. Clean
the mower before clipping plants, and disinfect the mower
with a bleach solution after each mowing. If TMVwas present
in a field in 2000, do not plant that field in tobacco in 2001
because undecomposed plant residue could result in infec-
tion of the new crop. Remember that TMV is spread by me-
chanical means, so touching a diseased plant before handling
healthy plants could result in new infections. The NC 297
variety has resistance to TMV and would be a good variety
choice if the disease was present in 2000.


EBW

New Touchdown Formulation

Syngenta is the newly formed company combining the crop
protection and seeds businesses of Novartis and Zeneca.
Syngenta has received registration of the new and Touch-
down non-selective herbicide which is crop-safe on all
Roundup Ready (RRTM) crops.

The new Touchdown has IQ TechnologyTM and is labeled for
over-the-top use in RR cotton, soybeans, and corn in addi-
tion to burndown applications. Touchdown 5, its predeces-
sor, was never registered in RR cotton or corn.

The new formulation combines a more efficient glyphosate
herbicide molecule with a balanced adjuvant delivery sys-
tem. The active ingredient in new Touchdown is diammonium
glyphosate (DA). Touchdown 5 contains glyphosate
trimedium (TMS or sulfosate), while Roundup and generic
glyphosates contain glyphosate isopropylamine (IPA).


The Syngenta News Release states that the IQ Technology
adjuvant delivery system overcomes four potential barriers
to consistent glyphosate weed control. First, it wets the leaf
surface and helps retain spray droplets on the leaf. Second,
it combats natural antagonism by neutralizing calcium and/
or magnesium ions in the spray water or from dust or on the
leaf surface. Third, it promotes increased penetration into
the leaf without damaging epidermal cells-allowing these cells
to actively transport the glyphosate herbicide throughout the
weed. Fourth, it enhances translocation throughvascular tis-
sue to the weed's shoots, roots, rhizomes, and stolons.

Syngenta advertises that no other adjuvants are needed with
the new Touchdown, and the rates of ammonium sulfate
(AMS), when used can be reduced by up to 25 percent com-
pared to other glyphosate herbicides. The common use rate
for controlling annual weeds is 1 quart per acre. It will be
110-gallon, 30-gallon, and 2.5-gallon containers. Pricing will
be comparable to Roundup Ultra Max.

(This information was taken directly from a Registration News
Release.)

JAT


Cover Crops for Strip Till Planting

Cover crops take time and are expensive to plant. However,
recent research has shown that they can add as much as 30%
to the yield of various crops. This can be economical for the
next crop, such as with cotton or peanut and is sustainable
long term by reducing erosion, adding organic matter, increas-
ing water infiltration, reducing sand blasting problems on
new seedlings, and preserving soil tilth. There are many more
benefits from cover crops. These covers need to be managed
properly. This may mean that a wheat cover has to have a
small amount of nitrogen applied in January or early Febru-
ary along with a broadleaf herbicide to kill winter weeds and
allow the wheat to head out prior to killing to plant into. This
size cover crop will moderate soil temperatures and keep soil
moisture higher throughout the growing season of the sum-
mer crop. Cover crops should be killed 3-4 weeks ahead of
planting to reduce cutworm, rootworm, and other soil insects
as well as to conserve soil moisture and allow the cover crop
to become brittle for ease of planting.


DLW

Crop Rotations

Bahiagrass in rotation with row crops increases crop yields
and profits. Economic models of cropping systems show that
it is much more profitable to include bahiagrass in rotation
with row crops than conventional cropping systems. Research
is underway to verify this under both irrigated and non-irri-








gated conditions. An interactive economics model is being
worked on along side this to allow growers to put in their
costs and returns for their situation.


DLW

PUBLICATIONS

The following publications have been recently UPDATED
and are available through EDIS. A PDF file for each publi-
cation is also available.

SSAGRO1 Weed Management in Tobacco 2001
SSAGR02 Weed Management in Corn 2001
SSAGR03 Weed Management in Peanuts 2001
SSAGR04 Weed Management in Cotton 2001
SSAGR05 Weed Management in Soybeans 2001
SSAGR06 Weed Management in Sorghum 2001
SSAGR07 Weed Management in Small Grain 2001
SSAGR08 Weed Management in Pastures and Rangeland-
2001
SSAGR11 Weed Management in Transgenic, Herbicide-
Resistant Soybeans 2001


SSAGR12 Florida's Organo-Auxin Herbicide Rule 2001
SSAGR14 Herbicide Prepackage Mixtures 2001
SSAGR15 Diagnosing Herbicide Injury 2001
SSAGR16 Approximate Herbicide Pricing 2001
SSAGR29 Tobacco Varieties for 2001
SSAGR100 Principles of Weed Management
SSAGR101 Application Equipment
SSAGR102 Calibration of herbicide Applicators
SSAGR103 Trade Name, Active Ingredient and Manufac-
turer of Some Herbicides
SSAGR104 Trade Names of Herbicides Containing a Given
Active Ingredient
SSAGR108 Using Herbicides Safely and Herbicide Toxic-
ity
SSAGR109 Adjuvants
SSAGR111 Weed Management in Fence Rows and Non-
Cropped Areas
SSAGR112 Poison Control Centers

The following NEWpublications are available through EDIS.
A PDF file for each publication is also available.

SSAGR88 Annual Ryegrasses


NOVEMBER CROP ESTIMATES


The National Agricultural Statistics Service made the following crop acreage and yield estimates
as of November 1:

Florida United States

Crop Acreage for Yield Acreage for Yield
Harvest (x1000) Per Acre Harvest (x1000) Per Acre

Cotton 92 420 lb 13,519 622 lb

Peanuts 80 2,450 lb 1,395.5 2,667 lb

Sugarcane 454 35 ton 1,026 34.7 ton

Tobacco 4.9 2,450 lb 492.3 2,289 lb

Corn, hay, soybeans, and wheat are no longer estimated for Florida. Cotton is carried over from
a previous forecast.


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
products.
Prepared by: J. M. Bennett, Chairman; E. B. Whitty, Extension Agronomist; C. G. Chambliss, Extension Agronomist, J. A. Tredaway, Extension
gronomist; and D. L. Wright, Extension Agronomist, North Florida Research and Education Center.