Title: Vegetarian
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Title: Vegetarian
Series Title: Vegetarian
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Creator: Horticultural Sciences Department, Institute of Food and Agricultural Sciences, University of Florida
Publisher: Horticultural Sciences Department, Institute of Food and Agricultural Sciences, University of Florida
Horticultural Sciences Department
Publication Date: February 1987
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Bibliographic ID: UF00087399
Volume ID: VID00230
Source Institution: University of Florida
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INSTITUTE OF FOOD AND
AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA


FLORIDA
COOPERATIVE
EXTENSION SERVICE


VEGETARIAN

A Vegetable Crops Extension Publication

Vegetable Crops Departmenct 1255 HSPP Gaincwille, FL 32611 Telephone 392-2134


Vegetarian 87-2


February 20, 1987


Contents
I. NOTES OF INTEREST

A. Vegetable Crops Calendar

II. COMMERCIAL VEGETABLES

A. Pounds Per Acre or Pounds Per Ton Are Growers
Applying the Correct Amount of Fertilizer?

III. PESTICIDE UPDATE

A. Screening pre and postemergence herbicides for
control of Parthenium (Parthenium
hysterophorus) Control.

B. Photodegradation of paraquat and glyphosate
applied to polyethylene mulch film.

IV. VEGETABLE GARDENING

A. Fertilizing the vegetable garden.


Note: Anyone is free to use the information in this
newsletter. Whenever possible, please give credit to the
authors.

The use of trade names in this publication is solely for
the purpose of providing information and does not
necessarily constitute a recommendation of the product.


The Institute of Food and Agricultural Sciences 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, or national origin.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS, STATE OF FLORIDA, IFAS, UNIVERSITY OF
FLORIDA, U. S. DEPARTMENT OF AGRICULTURE, AND BOARDS OF COUNTY COMMISSIONERS COOPERATING


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I. NOTES OF INTEREST


A. Vegetable crops calendar

March 14, 1987. State FFA Vegetable
Training Session. University of
Florida. (Contact J. M. Stephens).

April 21-22, 1987. Commercial
Vegetable Crops Extension In-Service
Training. Vanderbilt Inn, Naples
(Contact Don Maynard or Reggie Brown).

April 23, 1987. Commercial
Vegetable Crops Extension Program
Planning. Vanderbilt Inn, Naples
(Contact D. J. Cantliffe).

April 24, 1987. State FFA Vegetable
ID Contest. University of Florida.
(Contact J. M. Stephens).

May 7, 1987. Home Horticulture
Agents In-Service Training Session.
Gainesville.
(Contact J. M. Stephens).

June 22-26, 1987. State 4-H
Horticulture Institute. Camp Ocala.
(Contact J. M. Stephens).


II. COMMERCIAL VEGETABLES

A. Pounds per acre or pounds
per ton are growers applying the
correct amount of fertilizer?

One important step in proper
vegetable fertilizer management is a
soil test to determine exact
fertilizer needs. Another important
corollary is to apply the correct
amount of a fertilizer material to
achieve the optimum growth. One
common problem surfaces every year
regarding application rates. The
problem discussed below is particu-
larly acute with micronutrients.
Many growers use a fertilizer
blend with a "micronutrient package"
in it. It is usually expressed in
terms of "units per ton" or "pounds


per ton" and is a "shot-gun"
approach to fertilization. Let's
assume (and that's a big assumption)
that the grower really needs
micronutrients in his fertilizer.
Let's assume that the soil test
reflects a need for 2 pounds of
copper, 5 pounds of manganese, 1
pound of boron, and 5 pounds of zinc
per acre. The grower needs to apply
these amounts at planting along with
60 pounds of nitrogen, 120 pounds of
P205, and 60 pounds of K20 per acre.
His fertilizer dealer has the
following fertilizer for sale, the
tag of which is reproduced below:


Nitrogen (N) 6%
Phosphorus (P 0O) 12%
Potassium (K2 0) 6%
Boron (B) .02%
Manganese (Mn) .10%
Zinc (Zn) .10%
Copper (Cu) .05%


To achieve the correct N, P .,0
and K20 rates, he needs 1000 pounds
per acre. But what about the micro-
nutrients? At 1000 pounds per acre,
he is getting only 0.2 pounds of B,
1.0 pounds of Mn and Zn, and only
0.5 pounds of Cu per acre. If his
crop really needs these
micronutrients, the grower might be
in trouble.
The solution to the problem is
to work with the fertilizer dealer
to formulate a material that, when
applied at the proper rate, would
result in the desired amounts of all
nutrients in pounds per acre. A
better fertilizer material would be:


Nitrogen (N) 6%
Phosphorus (P 05) 12%
Potassium (K2 ) 6%
Boron (B) .10%
Manganese (Mn) .50%
Zinc (Zn) .50%
Copper (Cu) .20%


When applied at 1000 pounds per








acre at planting, this material can
supply what the grower needs.
Two points are apparent
regarding fertilizer use. 1) If
the grower really needs micro-
nutrients, he must be careful that
he has a fertilizer formulated to
suit his needs and that he applies
it at the correct rate to achieve
the needed nutrients in "pounds per
acre". "Pounds per ton" only tells
him the concentration of particular
nutrients in the fertilizer.
"Pounds per ton" equals "pounds per
acre" only when the fertilizer
material is applied at a rate of one
ton per acre. 2) The micronutrient
"package" concept can cause trouble.
If the grower arbitrarily purchases
a fertilizer with a "package", there
often is not enough micronutrients
present in situations when they are
really needed. If the grower
doesn't need micronutrients, then he
will be wasting money. Extra
micronutrients build up in the soil
and could become toxic to plants.

(Hochmuth Veg. 87-02)

III. PESTICIDE UPDATE

A. Screening pre and
postemergence herbicides for
control of Parthenium (Parthenium
hysterophorus) Control

Parthenium is rapidly becoming
a predominant weed pest in the Dade
County agricultural area. For a
description of the weed see Florida
Weed Science Society Newsletter Vol.
7, No. 2 or Vegetarian Newsletter
85-7. Commonly called pound cake
weed, santa maria, or dog-flea weed,
it does not appear to be as serious
a competitor as pigweed (Amaranthus
retroflexus) or spiny amaranth
(Amaranthus spiosus) because of slow
germination and early growth
characteristics. Thus for crops
that are commonly cultivated such as
snap beans or squash, control
through cultivation and crop


competition appear satisfactory.
Crops that are not commonly
cultivated such as in tomato row
middles where polyethylene mulch
culture is used or in tropical fruit
crops, parthenium weed pressure is
increasing. In tropical fruits, it
has become predominant and a
most-difficult-to-control weed pest.
In addition to the potential
for damage to agriculture,
parthenium produces contact
dermatitus and can cause severe
allergic skin reactions. This
dermatitus has been documented in
the United States, Australia, and
India. It has been called "The
Scourge of India" because of an
epidemic involving thousands of
adult males there.
Parthenium has become a major
problem in Dade County since about
the late 1970's. It apparently has
a wide range which includes the
coastal plains and adjacent
provinces from Florida to Texas and
as far north as Massachusetts, west
to Michigan and Oklahoma as well as
other geographic areas such as the
West Indies, Mexico, and Central and
South America.
Because of reports of poor
control of parthenium with some
herbicides and the fact that no
herbicides are currently registered
for parthenium, a series of
screening tests were initiated by R.
V. Tyson and H. H. Bryan to
investigate the efficacy of pre and
postemergence herbicides for the
control of this weed pest.
In screenings of selected
preemergence herbicides, 6
herbicides provided greater than 80%
control of parthenium for over 79
days. These herbicides were
metribuzin, atrazine, atrazine +
metolachlor (Bicep), linuron,
oxyfluorfen, and fomesafen. In
addition, imazaquin provided 96%
control for 42 days.
Results of experiments with
postemergence herbicides indicate
that paraquat applications alone







provide poor control of parthenium.
The control improves with greater
application rates, however, it
continues to be inadequate.
Diquat applications provide
satisfactory control and parthenium
control improved with increasing
rates of diquat in tank-mix
combinations with paraquat.
It was also noted that 7
herbicides applied postemergence
provided greater then 80% control of
parthenium for a period of 53 days.
These herbicides were fomesafen,
imazaquin, acifluorfen, bentazon,
dinoseb, metribuzin, and cyanazine.
Results of these experiments
indicate that there is reasonable
flexibility in selection of pre and
postemergence herbicides for
parthenium control assuming proper
labeling for these products can be
obtained.

(Tyson and Stall Veg. 87-02)


B. Photodegradation of
paraquat and glyphosate applied to
polyethylene mulch film

A common practice in the
production of polyethylene-mulched
crops is the broadcast, preplant
application of paraquat (Gramoxone)
to the polyethylene film and
uncovered row middles to kill
emerged weeds. In Florida, several
different colors of polyethylene
film are used with white and black
being the most common. Usually 2
weeks or longer pass after
application of the mulch before
transplanting operations begin,
during which time weeds can make
significant growth. Frequently,
rates of 1.0 lb paraquat/acre or
higher are required to kill these
weeds. Transplating often begins
within 24 hr after application of
herbicide. Injury similar to that
obtained with paraquat has been
observed on tomato and other crops
in Florida when transplanting was


followed by rainfall or heavy dew
with wind, causing contact of plant
foliage with the polyethylene film
(J. P. Gilreath, personal
observation). Generally, this
phenomenon has been observed when
transplanting and rainfall occur
within 3 days after paraquat
application. These observations
suggest that injury is due to
dissolution of paraquat residues on
the polyethylene film. Furthermore,
temporal decreases in injury suggest
that photodegradation of paraquat
residue alleviates the problem.
Paraquat also is used to kill
tomato vines at the end of the
season to eliminate potential
sources of disease innoculum for the
next season. This is especially
important at the end of the fall
crop as land preparation for the
spring season begins shortly after
the last harvest in many production
areas. When applied in this
fashion, considerable paraquat
residue remains on the mulch film.
The fate of this residue has become
increasingly important where double
cropping is practiced since planting
of the second crop, such as cauli-
flower or cucurbits, may follow the
clean-up operation by just a few
days.
Many growers in south Florida
have reported increased difficulty
in controlling seedling nightshade
with paraquat and in some fields,
torpedo grass has become a problem.
As a result, some growers have begun
using glyphosate (Roundup) to
control these weeds with application
made broadcast prior to transplant-
ing. Glyphosate is also used to a
limited extent for tomato vine kill,
particularly in the fall when vine
kill is sometimes more difficult to
effect with paraquat. Thus, both
paraquat and glyphosate residues may
present a significant problem to
growers when used as described.
Research has been conducted
over the past 2 years at the Gulf
Coast Research and Education Center








to determine a) if paraquat residues
could be responsible for the
observed injury to tomato, b) the
photodegradation rate of paraquat
residues on polyethylene mulch and
the associated decreased injury to
tomato, c) the effect of poly-
ethylene mulch color on paraquat
photodegradation rate, and d) the
photodegradation rate of glyphosate
under similar conditions as measured
by bioassay.
Paraquat: Duplicate replicated
experiments were conducted in
October and November, 1984 on black
and white polyethylene mulched beds.
Duplicate samples were taken 0 to
144 hours after application of 1
Ib/acre paraquat, one set for
quantitative analysis, while the
second set was used in a tomato
plant bioassay.
Results indicated no difference
due to mulch color. Substantial
injury was observed from 0 to 96
hours after application with 50% or
more crop loss anticipated until 120
hours (5 days) after application.
Paraquat residue from plastic 0 to
48 hours following application
reduced vigor to a point where if
the plants survived, a marketable
crop was not expected. From 120
hours on, plant vigor was acceptable
with very little crop loss expected.
Quantitative analysis indicated
60% of the applied paraquat was
recovered immediately after
application (275) ppm). The
greatest decrease in concentration
occurred in the first 24 hours,
dropping about 50%. Correlation of
concentration and vigor indicates
that apparently concentrations below
about 30 ppm of eluted paraquat are
not particularly injurious to 6-week
old tomato plants (120 hours).
Glyphosate: Experiments were
conducted in July, September, and
October of 1986 to determine the
duration of phytoactivity of
glyphosate residues when applied at
a rate of 1.0 lb/acre to white
polyethylene film mulch. Black


polyethylene mulch was not used
since previous work with paraquat
indicated mulch color had no effect
on paraquat photodegradation. The
sampling and bioassay procedure was
the same as that used for paraquat.
In July, samples were collected 1,
4, 8, 24, 30, and 48 hours after
application. This experiment was
terminated prematurely due to a
sudden rain storm washing the
polyethylene. In September, samples
were collected 6, to 168 hours after
application. The sampling interval
in the October experiment ranged
from 24 to 366 hours after
application with samples collected
every 24 hours.
Glyphosate photodegradation
rate decreased with each successive
experiment, presumably in response
to decreasing day length and
decreasing intensity of insolation.
Even after 48 hours, plant vigor was
less than 40% of that for untreated
plants in July; whereas, in
September, this had dropped to less
than 30% during the same time
interval. During the September
experiment, photodegration occurred
at a linear rate; however, not until
the last sampling period (168 hours)
had tomato plant vigor reached 70%
of that observed for untreated
plants. In October, all plants were
killed by residue during the first
48 hours after application. Even
after 336 hours, glyphosate residues
were still very injurious to young
tomato plants with vigor less than
30% compared to untreated plants.
Thus, growers who broadcast-
spray paraquat preplant at a rate of
1 lb/acre in mulched production
situations should delay planting 5
days after application to lessen the
chance of injury from paraquat
residue. Applications of greater
than 1 lb/acre would likely require
a waiting period longer than 5 days.
Preliminary analysis of data from
additional studies indicate an even
longer waiting period would be
required in January and shorter in








August.
If growers are using
glyphosate, a much longer waiting
period is indicated with a minimum
of 7 days during the longer days of
summer. Later in the fall and
winter, at least 2 weeks is required
for photodegradation and growers are
advised to exercise caution when
transplanting following such an
application.
Dew and rainfall can have a
very pronounced effect on the
photodegradation rate of both
herbicides when applied to poly-
ethylene mulch. Thus, if a grower
experienced no injury during a
period with rainfall or heavy dew,
he may be lulled into a false sense
of security only to later suffer
severe loss when little to no dew
and/or rainfall occurs.

(P. R. Gilreath, J. P. Gilreath and
S. J. Duranceau Veg. 87-02)

Ed Note: The following article by
P. R. Gilreath, Florida Cooperative
Extension Service, Palmetto, J. P.
Gilreath, Gulf Coast Research and
Education Center, Bradenton, and S.
J. Duranceau, University of Central
Florida, Orlando has been edited
heavily, especially in the material
and methods section to fit in this
publication. For those needing more
information on these experiments
please contact the authors.

(Stall)



IV. VEGETABLE GARDENING

A. Fertilizing the vegetable
garden.

The soon-to-be released
revision of Circular 104, Vegetable
Gardening Guide, includes a section
on fertilization and pH adjustment.
This section has been rewritten for
this revised edition by Dr. Gerry


Kidder, Extension Soil Scientist.
While there are no major changes, I
think it would be helpful to include
his section here so that it may
become familiar to all of us.
Adjusting soil pH The best pH
range for gardens on sandy soil is
between pH 5.8 and 6.3. When the
soil pH is below 5.5, an application
of 2 to 3 pounds of finely ground
dolomitic limestone per 100 square
feet will usually raise the pH
sufficiently. Lime should be
applied only when its need has been
established by a reliable soil test
such as the IFAS Home Lawn and
Garden Soil Test. Application of
lime when it is not needed may cause
plant nutritional problems.
Lime needs are best met 2 to 3
months before the garden is to be
planted. However, lime may be
applied as late as one or two weeks
before planting. Make sure the lime
is thoroughly mixed into the soil to
a depth of 6 to 8 inches, then water
to promote the chemical reaction.
Do not lime alkaline soils.
Instead, use garden fertilizer
containing the essential micro-
nutrients lacking under alkaline
conditions. Applications of sulfur
to slightly alkaline soils may be
helpful, but are of little benefit
on the high pH soils.
Fertilizing Unless very large
quantities of organic fertilizer
materials are applied, commercial
fertilizer is usually needed for
Florida gardens. Gardeners find it
convenient to use commonly available
fertilizer grades such as 6-8-8 or
15-15-15. Be sure to include micro-
nutrients if soil pH is above 6.3.
The quantities shown are usually
sufficient:









Fertilizer


Amount to
Broadcast


Amount to
Band on


Soil Grade on 100 sq. ft. 10 ft. of row

sand, marl
rock, or 6-8-8 2-5 lb. 5 oz.
clay 15-15-15 1-2 lb. 2 oz.

Organic soils 0-12-20 1-2 lb. 2 oz.
(muck or peat)


Broadcast the indicated amount
of fertilizer over the entire garden
plot one to two weeks before plant-
ing. Band the other portion at
planting time in 1 or 2 bands each 2
to 3 inches to the side of and 1 to
2 inches below the seed level or
plant row.
In addition, during the growing
season, it may be desirable to side-
dress 2 or 3 times with appropriate
fertilizer at half the banded rate
shown in the table. On mineral
soils, a grade such as 15-0-15 may
also be used for sidedressing at a
rate of 1/2 to 1 oz. per 10 ft. of
row. Side dress just beyond the
outside leaves.
If a different fertilization
recommendation accompanies your soil
test, use those specific recommen-
dations rather than the general ones
given here.


My comments: With both the old
and revised guidelines, it is
necessary for gardeners to calculate
the area occupied by a given
vegetable. The gardener should
broadcast (scatter) up to 5 pounds
of fertilizer over the calculated
area. Additional fertilizer then
should be banded on the basis of row
length and fertilizer grade.
Obviously, there are several
modifications that can and do work
out satisfactorily. In some cases,
all of the fertilizer is broadcast
before planting. In other
situations, all is banded, either on
one side or on both sides of the
row. Some gardeners use liquid
fertilizer poured at the base of
each plant. The point is that our
guidelines are not that rigid, but
they do serve as the basis for a
good sound fertilization program in
most instances.


(Stephens, Veg. 87-02)

Prepared by Extension Vegetable Crops Specialists


Dr. D. J. Cantliffe
Chairman

Dr. G. J. Hochmuth
Assistant Profes

Dr. S. M. Olson
Associate Professor


Dr. D. D. Gull
Associate Professor

Dr. D. N. Maynard
Professor

Dr. W. M. Stall
Professor


Dr. J. M. Stephens
Professor




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