A Vegetable Crops Extension Publication
Horticultural Sciences Department P.O. 110690 Gainesville, FL 32611 Telephone 904/392-2134
May 12, 1995
I. NOTES OF INTEREST
A. Vegetable Crops Calendar.
I. COMMERCIAL VEGETABLES
A. N Fertilization of Carrots on Mineral Soil.
B. Summer Squash Variety Evaluation Spring 1994.
C. Less is More.
D. Recent Innovations in Strawberry Cooling and Handling.
III. VEGETABLE GARDENING
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UNIVERSITY OF Cooperative Extension Service
'F LORIDA Institute of Food and Agricultural Sciences
I NOTES OF INTEREST
A. Vegetable Crops Calendar.
May 25, 1995. Organic Gardening
Field Day, 10:00 AM 12 noon. Organic
Park, Fifield Park, UF. (Contact J. M.
I. COMMERCIAL VEGETABLES
N Fertilization of Carrots on
Florida carrots are grown on the
Histosols of central and southern Florida.
There are, however, a few growers in northern
Florida and southern Georgia growing carrots
on sandy soils. Little information is available
on fertilization of mineral soil carrots and
resulting chemical quality. Mark Bassett and
I have discussed the idea of mineral soil carrot
production in the winter in northern Florida.
Our idea was to investigate the yield and
quality potential for winter fresh market
carrots. JeffBrecht has agreed to analyze the
roots for carotenoid and sugar concentrations.
Three plantings were made in mid
November, December, and January of
'Choctaw' imperatorr type) and 'Scarlet
Nantes' (Nantes type). Carrots were seeded in
twin rows on 24-inch-wide beds on four-foot
centers and thinned to one inch between plants
when one inch tall.
Nitrogen and potassium fertilization
effects were investigated using rates of N and
K20 ranging from zero to 200 Ib per acre in
50-lb increments. N or K20 was applied at 20
lb per acre at planting and the remainder was
applied in three sidedressings banded in the
center of the bed. All carrots in the N test
received 150 lb K20 per acre and all carrots in
the K test received 150 lb N per acre.
Carrots were dug, washed, topped, and
graded. Figure one summarizes the responses
of carrots to N fertilization. We will present
the results of the K tests later. Figure one has
the results of the first two plantings, the third
one is yet to be harvested. Carrot yield
responded dramatically to N fertilization, but
yield leveled off after 100 lb N per acre.
Results clearly show that our new
recommendation of 150 lb N per acre is ample
N for mineral soil carrot production and that N
rates higher do not increase yield, but may
even reduce yield.
N FERTILIZATION OF CARROTS ON
YIELD, TOPPED, US NO 1 OR BETTER (LBIACRE)
0 50 100 150
N RATE (LBIACRE)
nantes-1 nantes-2 choc-1 choc-2
--- -- -*- --
(Hochmuth, Vegetarian 95-05)
B. Summer Squash Variety
Evaluation Spring 1994.
During the 1992-93 crop year, 12,300
acres of summer squash were harvested in
Florida. Average yields were 276
bushels/acre, total production was about 3.4
million bushels which sold for $9.20 per bushel
amassing a total crop value of just over $31
million. About a third of the crop was grown
in Dade County, but central Florida accounted
for about 25% of the acreage.
This trial was arranged to evaluate
performance of some yellow straightneck and
crookneck hybrids and some zucchini hybrids
which were developed at the Central Florida
Research and Education Center with
commercial hybrid summer squash varieties at
Bradenton and Leesburg.
The EauGallie fine sand was prepared
in early March 1994 by incorporation of 0-1.2-
0 lb N-P,20-K20 per 100 linear bed feet (Ibf).
Beds were formed and fumigated with
methylbromide:chloropicrin, 67:33 at 2.3
lb/100 lbf. Banded fertilizer was applied in
shallow grooves on the bed shoulders at 2.7-0-
3.8 lb N-P205-K20/100 lbf after the beds were
pressed and before the black polyethylene
mulch was applied. The total fertilizer applied
was equivalent to 130-60-182 lb N-P205-
K,0/A. The final beds were 32 in. wide and 8
in. high, and were spaced on 9 ft centers with
four beds between seepage irrigation/drainage
ditches which were on 41-ft centers.
In Leesburg, Apopka fine sand was
prepared in February by incorporation of 0.8-
1.1-1.1 lb N-P205-K20 per 100 linear bed feet
(lbf). Beds were formed, black polyethylene
mulch, and drip tubing were applied in one
operation. Emitters were spaced 12 in. apart
on the drip tubing. The final beds were 24 in.
wide and 8 in. high and were spaced on 10 ft
centers. The total fertilizer applied, including
that supplied through the drip irrigation
system, was equivalent to 140-80-160 lb N-
P,20-K20/A. Drip irrigation was supplied as
needed based on soil tensiometer readings.
Squash seeds of 21 entries were
planted in holes punched in the polyethylene
mulch at 2.5 ft in-row spacing on 4 March at
Leesburg and 18 March at Bradenton. The
plots were 12.5-ft long, had five plants each,
and were replicated four times in a
randomized, complete block design. Weed
control in row middles was by cultivation and
application of paraquat. Pesticides were
applied as needed for control of silverleaf
whitefly endosulfann and esfenvalerate), and
Squash were harvested 9 times
between 15 April and 5 May at Leesburg and
11 times between 22 April and 16 May at
Bradenton. Marketable fruit (U.S. No. 1 or
better) according to U.S. grades were
separated from culls and counted and weighed.
Plants were rated from 1 (least
resistant) to 5 (most resistant) for powdery
mildew on 11 May at Bradenton. The
designation of individual ratings was 1 = 75-
100% of the main stem covered with powdery
mildew colonies, 2 = 50-75% covered, 3 = 25-
50%, 4 = 1-25%, and 5 = 0 powdery mildew.
In Leesburg, plants were rated
powdery mildew and virus resistance on a
scale of 1, least resistant, to 5, more resistant.
Virus in the fruit was based on the percentage
of fruit, culled due to virus infection.
Bradenton. The most resistant lines to
powdery mildew within each squash type
were: straightneck D42-2 x E34, D43-1 x
E34, Early Prolific', and 'Multipik'; crookneck
- E40-7 x E43, E39-1 x E42, 'Tara', 'Bandit'
and 'Supersett'; and zucchini D34-3 x D33
and D36-7 x D33. A high level of powdery
mildew resistance was not always associated
with high yields.
Within the straightneck types, the early
yields ranged from 108 bu/acre for 'Precious'
to 269 bu/acre for D43-1 x E34. Total yields
ranged from 308 bu/acre for 'Precious' to 661
bu/acre for 'Multipik'. Three other entries had
yields similar to those of 'Multipik'. In the
crookneck types, early yields ranged from 70
bu/acre for 'Tara' to 280 bu/acre for
'Medallion'. Total yields ranged from 340
bu/acre for 'Tara' to 640 bu/acre for
'Medallion'. Six other entries had yields similar
to those of 'Medallion'. In the zucchini type,
early yields ranged from 44 bu/acre for D36-7
x D33 to 214 bu/acre for 'Zucchini Elite'.
Total yields varied from 58 bu/acre for D36-7
x D33 to 407 bu/acre for 'Zucchini Elite'.
Three other entries were similar in yield to
'Zucchini Elite'. Yields obtained in this trial
can be compared with a 1988-89 to 1992-93
state average yield of 313 bu/acre.
Accordingly, 18 of the 21 entries exceeded the
five-year state average yield. Yields of a
yellow summer squash trial at this location in
1993 ranged from 532 to 811 bu/acre.
Two of the experimental yellow
straightneck hybrids D43-1 x E34 and D42-2
x E34 and one of the experimental zucchini
hybrids D36-7 x D33 bore fruit that were too
short and too broad in diameter (data not
shown) to be commercially acceptable. The
other experimental hybrids bore fruit that was
Leesburg. Powdery mildew did not
appear until late in the growing season. In
straightneck squash, the open pollinated
variety, 'Early Prolific Straightneck', appeared
to be more susceptible to powdery mildew
than the hybrid varieties. In the crooknecks,
E40-7 X E43 had no powdery mildew. In the
zucchini types, all entries had good resistance
except 'Elite' and D34-3 X D33.
Virus was severe during this season
and all of the entries were susceptible. In the
yellow squash, virus infection in the fruit
ranged from 17% to 39%. Zucchini fruit were
less affected by virus. In summer squash total
yield ranged from 150 bu/acre to 301 bu/acre.
Differences among the yellow squash entries
were generally not significant which may have
been the result of severe virus infection. It
appeared that the three entries from Leesburg
and 'Precious' might have better yield than the
other straightneck entries. 'Tara', Dixie', and
the entries from Leesburg had lower yield than
the other crookneck entries. D36-7 X D33,
'Ambassador', and 'Elite' generally had better
yields than 'Seasons', 'Viceroy', and D34-3 X
Entries with high levels of powdery
mildew resistance at both locations were D42-
2 X E34, E40-7 X E43, and D36-7 X D33.
Yields were considerably higher at Bradenton
than at Leesburg, probably because of the
severe virus infestation at Leesburg. Also,
perhaps because of the virus infestation, there
was little agreement in performance of the
entries at the two locations.
(Maynard and Elmstrom, Vegetarian 95-05)
C. Less Is More.
A few days difference in timing can
make a world of difference in price, therefore
grower philosophy on harvesting is usually
"the earlier the better". Re-examining the
results from one of our tomato "soap"
phytotoxicity studies in the early '90's, we
noted something of interest ... pesticide
applications can delay tomato fruit maturity!
Recapping the test, we transplanted
tomatoes in early fall 1992 in Immokalee. We
subjected these plants, once weekly, to
individual applications of either liquid
detergent at one of two rates or a conventional
insecticide tankmix (2 products) in rotation
with an additional insecticide product. A
preventative fungicide program (once or twice
weekly depending on disease pressure) and
BT's were applied to all plants.
The treatments were applied for a
period of 11 weeks before harvests were
begun. The industry standard, "5% color",
was used as the harvest criteria. Harvested
fruit were separated into reds and greens and
graded by size and number. "Reds" were
considered any fruit of category 2 or greater.
Both the soap treatments and the
conventional insecticide spray influenced
tomato maturity and extra-large size
production at first harvest, compared to the
plants that did not receive insecticides (Table
1). Untreated plants produced more extra
large red fruit and more total red fruit at first
harvest than soap at 0.25% or 1.0%, and the
conventional insecticide program. Greater
quantities of red fruit on the unsprayed plants
suggested that they had reached maturity
sooner than sprayed plants.
Table 1. Effect of detergents and conventional insecticides on 'Sunny' tomato fruit maturity at first
harvest in Fall 1992.
Red Fruit Yield (lbs/plant)
Treatment Extra large Total
No Insecticide Applied 4.87 a 5.25 a
Detergent @ 0.25% 1.28 b 1.46 b
Detergent @ 1.0% 2.29 b 2.53 b
Conventional Insecticides* 1.79 b 2.25 b
This program included a tankmix (2 conventional products) in rotation with another conventional
product as a once-weekly spray.
Do our results represent a real impact
of spray programs on maturity? More tests
must be run, however, if this relatively "low-
input" program can influence maturity so
greatly, think what some grower programs
must be doing!
We don't suggest suspending all
pesticide applications of course. This test was
conducted under relatively low pest
conditions. Yet our results should emphasize
the need for an as needed program based on
scouting and stimulate thinking about more
sustainable approaches to crop production.
We have further studies planned for the
coming fall to test the hypothesis of "spray and
delay" so we will keep you posted. But from
what we've seen so far the old adage seems to
hold true ... less is more!
(Vavrina & Stansly, Vegetarian 95-05)
D. Recent Innovations in
Strawberry Cooling and Handling.
Part 2. Sensitivity to Bruises
Field packing is the primary method
employed in commercial production areas in
the U.S., having been adopted to reduce
mechanical injury by minimizing handling
steps. Although bruising was reduced, field
packing has limited flexibility for producing
and marketing value-added specialty packs
such as the clamshell package or selecting
extra-large fruits with attached stems. The
main drawback is that the entire quality control
program depends on the ability and motivation
of the pickers to perform many tasks in the
field, ranging from determination of ripeness
stage and fruit quality to removal of diseased
fruits, harvest, placement in the package and
delivery to a field wagon. All of these
operations must be performed by each picker
without bruising the fruit while maintaining a
consistently high quality level under strenuous
conditions. In order to be able to meet the
growing demand of specialty packs,
strawberry handling must be modified to
permit more uniform grading without
increasing mechanical injury.
Since losses of strawberries at the retail
level have be correlated with mechanical
injury, we determined the relationships
between fruit temperature and susceptibility to
compression and impact bruising.
Compression bruising occurs over time due to
pressure from static weight bearing down on
the fruit, during handling and shipping. Impact
bruising develops following the occurrence of
a sudden force such as a drop.
We found that compression and impact
forces had opposite effects on bruise incidence
when strawberries were at ambient (24C) or
low (1C) temperatures. When tested at
ambient temperature, strawberries were more
resistant to impacts, while at the lower
temperature, the fruits were more resistant to
The results from these studies indicate
that postharvest strawberry quality may be
significantly extended by adoption of a novel
handling system with the following features.
Strawberries would be harvested into reusable
field flats during the cooler times of the day;
this would provide greatest resistance to
compression bruising during field handling to
a central packing facility. There the fruits
would be transferred to a specially built
grading line via a chlorinated, hydrohandling
system, then graded, hydrocooled in bulk or in
containers, palletized and treated with
modified atmosphere packaging for shipping.
Strawberries should be cooled after sorting
and grading since they are more resistant to
impact bruises at ambient temperatures.
Further tests are required to select appropriate
handling components which would make such
a system feasible.
(This article was condensed from a
presentation made at 4th North American
Strawberry Conference held in Orlando 15-17
(Sargent, Vegetarian 95-05)
m. VEGETABLE GARDENING
This is the last of my three articles on
earthworms and gardening to appear in this
newsletter. The first two were
Vermitechnology (March, 95) and
Vermigardening (April, 95). Much of the
information for these articles has been
provided by vermitechnologist Larry Martin
who runs an earthworm farm in Orange Lake,
Marion County, Florida. Those of you
attending the Organic Gardening field day on
May 25 at Gainesville will have an opportunity
to meet Mr. Martin as he demonstrates the use
of earthworms in gardening.
Vermicomposting is a natural bio-
decay process in which bacteria, fungi, and
other micro-organisms in the soil break down
organic material so that it may be consumed
and further broken down by earthworms. It is
somewhat like regular composting taken to a
final stage of decomposition that yields a
fertile organic soil called worm castings.
The ideal vermicompost bin size is 12
inches high, by 3 feet wide and 8 feet long.
Actually, it may be of any width and length,
but the height should never be more than 16
inches, which is rather low as compost bins go.
Use 2 x 12 pressure treated wood with
/2 inch wire mesh attached to the bottom. The
wire mesh is very important to prevent the
intrusion of unwanted rodents. Moles, for
example, are known to consume their weight
in worms each day.
Entry from the bottom is not the only
concern, as racoons, armadillos, birds and
other varmints (including pets) can be a
problem from the top. For prevention,
construct a hinged cover made of the same
size mesh wire attached to a frame that may be
Most any thing growing in the yard is
potential food for the earthworms (red
worms), bacteria fungi, and other
decomposers. As with all types of
composting, a balanced ration of carbon to
nitrogen in the content of organic materials is
important. One easy way to obtain this needed
balance is to provide two parts green material
(nitrogen provider) to one part brown (carbon
provider). A thorough mixing will help speed
the decomposition process. Also, it is best to
first chop up or shred the yardwaste before
adding them to the bin and mixing.
Examples of nitrogen-rich materials are
fresh grass clippings, plant trimmings,
especially legumes, vegetable matter, and
animal manures Examples of carbon-rich
materials: dry leaves, straw, yard waste
compost, and small amounts of sawdust.
Preparing bin for the worms
Three to four days before introducing
the wonns to the pile, spread a layer (6 to 8
inches thick) of any combination of the organic
ingredients just mentioned. To this you may
add up to 25% of the total mixture as ground
up newspaper or corrugate, as the worms love
the glue in the mix. Water heavily for 3-4
days, then make sure the materials have
"heated out" and cooled before adding the
Adding the earthworms
The red worms (Eisenia fetida) are
introduced by spreading them over the entire
area of freshly watered organic matter in the
bin in the early or mid-morning. The worms
will crawl into the soil rapidly. You need
about 200 earthworms per square foot of bed
After settling down, the earthworms
will feed on the bedding and will come to the
surface for feed. Use only the nitrogenous
materials as feed. Place it on the surface,
except for kitchen scraps which should be
placed down 3-4 inches and covered with
bedding (eliminates rodents, flies and odors).
Add water (between periods of rains)
to provide adequate moisture for the surface-
feeding worms. Moisten the surface without
soaking the entire bed depth.
It is best to locate the bin out of direct
full sunlight (70 80F is good range).
Red worms double their number every
2 months. If the bin compost worms are not
harvested, the worms leave in search of food
and may enter your lawn or garden as well to
benefit that area.
(Stephens, Vegetarian 95-05)
Prepared by Extension Vegetable Crops Specialists
Dr. D. J. Cantliffe
Dr. S. M. Olson
Mr. J. M. Stephens
Dr. G. J. Hochmuth
Dr. S. A. Sargent
Dr. C. S. Vavrina
Dr. D. N. Maynard
Dr. W. M. Stall
Professor & Editor
Dr. J. M. White