INSTITUTE OF FOOD AND
UNIVERSITY OF FLORIDA
A Vegetable Crops Extension Publication
Vegetable Crops Department 1255 HSPP Gaincsville, F 32611 Telephone 392-2134
January 10, 1984
I. NOTES OF INTEREST
A. New Publications
B. Vegetable Crops Calendar
II. PESTICIDE UPDATE
A. Sonalan Labeled on Watermelon, Cucumbers, and
III. COMMERCIAL VEGETABLE PRODUCTION
A. Injection Of Fertilizers Into Drip Irrigation
Systems For Vegetables
B. Factors Affecting The Replanting of Cold Damaged
IV. HOME VEGETABLE PRODUCTION
A. Florida Master Gardeners Begin A New Year
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COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS, STATE OF FLORIDA, IFAS, UNIVERSITY OF
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I. NOTES OF INTEREST
A. New Publications
Vegetable Variety Trial Results in Florida for
1982, Experiment Station Circular S-306 is
available from IFAS Publication, Bldg. 440, Univer-
sity of Florida, Gainesville, 32611.
B. Vegetable Crops Calendar
1. January 17, 18, 19 The 37th Annual Meeting of
Southern Weed Science Society, Arlington Hotel,
Hot Springs Arkansas. The theme this year is:
Biotechnology and Weed Science.
2. January 26, 4pm-9pm North Florida Watermelon
Meeting, Newberry High School Auditorium.
3. February 8-10 Florida is hosting Weed Science
Society of America at the Hyatt Regency Hotel,
4. February 15-16 Third Annual Florida Seedsmen's
Seminar, Ramada Inn, Ocala.
5. April 18, 1984 1 pm, Immokalee Field Day
6. February 28 and 29 The Seventh Annual Meeting
of Florida Weed Science Society Gainesville.
7. September 6 Tomato Institute, Marriott Hotel,
II. PESTICIDE UPDATE
A. Sonalan Labeled on Watermelon, Cucumbers and
Ethalfluralin (sonalan) has been labeled for
the control of certain broadleaf weeds and annual
grasses in watermelon, cucumbers, and muskmelons.
Application should be made at 3 pts/A material,
surface applied, preemergence to the crop (post-
plant). Rain or overhead irrigation is required
within 7 days. Do Not Incorporate Mechanically.
Sonalan should be available for this spring's crop.
Read the label and follow the directions for use.
(W. M. Stall)
III. COMMERCIAL VEGETABLE PRODUCTION
A. Injection of Fertilizers into Drip Irrigation
Systems for Vegetables
In recent years, commercial vegetable growers in
Florida have shown increased interest in drip (trickle)
irrigation as a means of irrigating their vegetable
crops. Drip irrigation, the newest of all the commercial
irrigation methods, is the frequent, slow application of
water to soils in the plant's root zone through small
holes in the water delivery line or from mechanical de-
vices (emitters) attached to the water delivery line.
Drip irrigation is not only an irrigation method, but al-
so can be utilized as a means by which plants can be sup-
plied with supplementary soluble materials such as ferti-
lizers, fumigants, insecticides, or herbicides. The pro-
cess of adding soluble fertilizer through the drip system
is called fertigation. The advantages of applying ferti-
lizers through the drip irrigation system are improved
fertilizer use efficiency, labor savings, energy savings,
and greater flexibility in timing nutrient applications
to meet a crop's demand for nutrients. With the capabi-
lity to inject fertilizers through the drip irrigation
system, fertilization can take place at any time, regard-
less of a crop's growth stage or the accessibility of the
field to machinery. Fertilizers which are injected into
the drip irrigation system versus the spreading/
broadcasting method with dry materials are more effi-
ciently utilized because a smaller amount of fertilizer
is in the soil at any particular time and therefore, less
susceptible to loss from leaching and run-off during
heavy rainfall. Fertilizers which are injected into the
drip irrigation system present less danger of injuring
the plant's root system, since the liquid fertilizer is
greatly diluted in the irrigation water.
Elements That Can Be Applied
Through Drip Irrigation Systems
Nitrogen (N) is the most frequently injected element
into drip irrigation systems, as it is readily leached
from sandy soils and must be applied to maintain good
crop growth. N is generally injected into the system
as ammonium nitrate, calcium nitrate, or potassium
nitrate. The pH of the irrigation water should be known
at the time of fertilizer injection since some N sources
will increase the pH of the water. By increasing the pH
of the water, the threat exists of precipitation of
insoluble calcium and magnesium carbonates present in
some water sources that can clog the drip irrigation
Injection of phosphorus (P) into drip irrigation
systems is generally not recommended because (1) properly
applied preplant P satisfies the plants P needs, 2) the P
injected into the drip system is a clogging hazard to
emitting orifices, and 3) because of the restricted move-
ment of P in the soil.
Potassium (K) is also easily leached in sandy soils
and generally must be applied with N to maintain good
crop production and quality. K can be injected into the
drip irrigation system as potassium sulfate, potassium
chloride, or potassium nitrate.
Generally, micronutrients can be applied preplant
for most crops and in most soils. Iron, copper, zinc,
and manganese may react with the salts in the irrigation
water and precipitate. The chelated forms of iron or
zinc EDTA, which are more soluble than the non-chelated
forms, usually cause little clogging problems and are
preferred over the previously mentioned salts when this
application is needed.
The three principal methods utilized to inject fer-
tilizers into drip irrigation systems are pressure dif-
ferential, the Venturi (vacuum) and metering pumps. It
is essential that drip irrigation systems equipped with a
chemical injection system have a vacuum breaker (anti-
siphon device) and a backflow preventer (check valve) in-
stalled upstream from the injection point. The vacuum
breaking valve and backflow preventer will prevent chemi-
cal contamination of the water source in case of a water
pressure loss or power failure.
General Fertilization Procedures
1. Approximately 30-40% of the N and K, and 100% of
the P, secondary elements (Ca, Mg, and S) and
micronutrients should be applied in to the plant bed.
This fertilizer should be applied as a 50% broadcast
application in the bed. Fertilizer placement in drip
irrigated beds has not been determined for each of the
commercial vegetable producing areas in Florida. The
incorporation of fertilizers into the plant bed has been
shown to be better than banding on the soil surface. If
fertilizer is banded in the plant bed, the fertilizer
band must be within the wetting pattern. The remaining
60-70% of the N and K should be injected into the drip
system during the growing season.
2. Fertilizers may be injected into the drip irri-
gatation system on a daily, bi-weekly, or weekly basis.
3. The quantity of fertilizer to inject will depend
on the growth stage and rate of growth of the crop.
A research study on drip irrigation of tomatoes was
conducted where N and K (60% of the total season
requirement) were injected weekly with the following
percentages of the total injected N and K being injected
each week (14 week crop); 0, 2, 4, 6, 8, 12.5, 12.5,
12.5, 12.5, 7.5, 7.5, 7.5, 7.5, and 0%.
4. The drip irrigation system should be allowed to
reach its working pressure prior to the injection of the
fertilizer solution. The actual time for the fertilizer
injection interval should be not more than 80% of the ir-
rigation interval. The short span of time (20% or more
of the irrigation interval) is left at the end of the
fertilizer interval to allow for flushing of the ferti-
lizer pump and the irrigation system.
5. Fertilizers should not be injected at the same
time that pesticides or chlorine (liquid bleach) are be-
ing injected. Chlorine (liquid bleach) is injected into
the drip irrigation system to prevent the formation
of bacterial slimes and iron deposits which can clog
emitting orifices of drip irrigation systems. Chlorine
should be injected following the injection of fertilizers
with the injection interval being long enough to permit
30 minutes of chlorine to reach the last emitter. For
example, if it takes 15 minutes for the chlorine to reach
the last emitter, then the total time for chlorine to be
injected will be a minimum of 45 minutes (15 minutes plus
30 minutes). The frequency of chlorination and quantity
of chlorine to inject depends on various water quality
factors (pH, and concentrations of iron and hydrogen sul-
fide). For further information on the frequency of
chlorination and quantity of chlorine to inject, growers
need to contact their local Florida Cooperative Extension
Service (IFAS) office.
In conclusion, the Institute of Food and Agricul-
tural Sciences (IFAS) of the University of Florida,
through research and extension programs, plans to con-
tinue to assist vegetable producers and irrigation indus-
try personnel in meeting the technological changes taking
place in the area of waters and fertility management.
With the introduction of drip irrigation and its accom-
panying advantage in cultural management (fertigation),
the challenge exists to adapt and maximize drip irriga-
tion according to Florida's growing conditions.
B. Factors Affecting The Replanting Of Cold Damaged
The December freeze damaged in some form much of the
vegetables in production in the state. Unfortunately,
and/or fortunately, depending on which way you look at
it, we do have experience on replanting decisions and
choices that the growers must make.
The first and foremost caution is do not overplant
and cause a market glut. In the southern portion of the
state it is not too late to direct-seed and produce toma-
toes, peppers and eggplant for a timely market. The mad
scramble for transplants is now probably over, also with
growers looking for other choices.
Choice 1: Procure transplants from other states or
Mexico. Historically, this is not the best choice. The
transplants coming from other states and especially
Mexico have to be inspected before entering the state.
The Florida Department of Agriculture and Consumer Ser-
vices, Division of Plant Inspection is responsible for
For information on inspection procedures from dif-
ferent areas or to set up inspections contact:
North Florida: (904)372-3505, Gainesvlle
Central Florida: (305)886-4375, Apopka
South Florida: (305)251-9540 or 238-6561, Miami
State Office: (904)372-3505, Gainesville
Choice 2: Plant alternate crops. This is an excel-
lent way to use the fertilizer and cultural expenditures
already invested. The big caution here is to check on
whether there will be a market for the crop at the time
of harvest. A few growers found to their sorrow in past
years that the alternate crop they chose to grow either
could not be harvested due to lack of a market caused
both by a glut and in other cases no demand and lastly,
lack of transportation.
Other growers were able to recoup their losses and
make a profit on alternate crops sold nationally and lo-
Choice 3: "Suckering" to produce at least partial
crops. After the 1977 freeze this method worked supris-
ingly well. The methods followed were based on the de-
gree of damage to the plant and consisted of hand prun-
ing, mowing plants back to a stump and in a few cases
leaving plants untouched. Eggplants responded more uni-
formly then did tomatoes or peppers, producing higher
quality fruit. In tomatoes, varieties responded differ-
ently in fruit sizing, after suckering. In pepper,
plants recovered satisfactorily but did not produce the
blocky, "crown-pick" type of fruit. They did grade out
with a high percentage of fancy fruit however.
In areas where crops were completely destroyed and
replanting or reseeding of the same crop or alternate
crops can be made there are several factors that should
be kept in mind:
1. Fertility (Rates and Placement)
Refertilization may raise the soluble salt
levels in a field to an excess and cause damage
to the young seedlings.
Here again be careful not to overdo it.
Also, in planting alternate crops check the tol-
erance of the crop to previously applied herbi-
cides. Alternately, herbicides applied to the
alternate crop may not be compatible with pesti-
cides such as nematicides applied to the first
3. Crop and Variety Selection
Don't plant any old crop just because seed
or transplants are available. Check for market-
ability and suitability for the area before
4. To Plant or Not to Plant
The winter isn't over yet and there are
possibilities for other frosts and freezes.
A decision should be made by each grower,
depending on his situation, whether the invest-
ment output is worth the gamble in replanting.
In many cases where all the grower's plantings
were not destroyed, it may be more efficient and
a wiser choice to protect the remaining crop,
which should be assured a decent market price,
than to replant and possibly over extend himself
and lose both.
Another problem could blossom, if you'll
forgive the pun, from the extended cold period.
This is the vernalization of many cool sea-
son crops. Vernalization is the specific promo-
tion of flower initiation by a previous cold
treatment. The vernalization requirements of
each crop vary with the number of hours below a
certain temperature, the stage of maturity of
the crop and in some cases the day length. Ver-
nalization requirements also vary among culti-
vars within a crop. An example of this is the
early cultivars of celery being prone to bolt-
ing. The newer cultivars have been selected in
many cases to have a higher tolerance.
Lettuce will probably bolt more rapidly
when the temperatures begin to warm, now that it
has had an exposure to a long cold period. On
the other hand, some crops could be devernalized
by a significant temperature increase.
Growers of celery, cabbage and other cruci-
fers, lettuce, carrots, etc. should be aware of
the possibility of their crop being vernalized
and thereby keep an eye on it during its devel-
(W. M. Stall)
IV. HOME VEGETABLE GARDENING
A. Florida Master Gardeners Begin a New Year
1984 marks the sixth year for the Master Gar-
deners program in Florida. The first classes were
held in the pilot counties of Brevard, Dade, and
Manatee in 1979. Since then 29 counties have par-
ticipated in the training of these specialized vol-
unteers we call Master Gardeners.
Last fall (1983), eight counties participated in
training. A joint session was held in Jacksonville
where Master Gardeners from Clay, Duval, Putnam and
St. Johns received the training together. Agents in
Alachua, Highlands, Marion, and Volusia conducted
training by themselves.
Thirteen counties are scheduled to hold training
this spring (1984). Flager and Escambia are two
newcomers to the program. Hillsborough, Manatee,
and Pinellas are combining in a unique method of
training, meeting in each county on a rotational
basis. Charolotte and Lee are getting together in a
somewhat similar way by training one day in Lee and
the next in Charolotte. Those planning to go it
alone are Brevard, Dade, Escambia, Flagler, Leon,
Martin, Osceola, and Palm Beach.
The continuing expansion of the program into
more and more counties speaks well for the overall
success and acceptance of the program in Florida.
In just five years, almost 1/2 (43 percent) of
Florida's counties have adopted the program. As ex-
pected, agents in the major urban areas have been
more anxious to tap the energies of volunteer Master
Gardeners than their more rural counterparts.
While the Master Gardeners have served in a
variety of useful roles in the educational programs
of the separate counties, by far the greatest use of
their talents has been in answering individual home
horticulture questions via telephone, clinics, or
Agents wishing to initiate a Master Gardener
program should get in touch with me for all of the
(J. M. Stephens)
Prepared by Extension Vegetable Crops Specialists
locatee W.M. Stall
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