The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
TUive-rsity of jorida
SUB-T2OPICAL TfERIa-rT STATION
SOME ACCOMPLISHMENTS OF THI SUB-TROPICAL EXPERIMENT STATION
DURING ITS NINE YTERS OF EXISTENCE
W. M. Fifield
e Sub-Tropical Experiment Station, established in the fall of 1930, is
he four branch stations of the University of Florida's Agricultural
at Station system, of which Dr. Wilmon Newell is Director. Other branch
are the Everglades Station at Belle Glade, the Citrus Station at Lake
ind the North Florida Station at Quincy,. The West Central Florida Station
wville is maintained by the United States Department of Agriculture, but
.ts are in cooperation with the Florida Station. In addition to the
tions, eight field laboratories are also maintained at various points
.te. The Main Experiment Station is located at the University in
office and laboratories of the Sub-Tropical Experiment Station are
a Waldin Drive one-quarter mile west of Redland Road. Here, on the rock-
iddition to administrative and laboratory activity, is maintained a
experimental farm for avocado, citrus, mango, forestry, cover crop and
.eous subtropical fruit and ornamental research. Another farm consisting
-res of marl is located about 6 miles east of Homestead on the North Canal.
knownn as the Station:s East Glade farm, and here is conducted most of the
eld research, and also tests with other vegetables and cover crops. A
Le 30-acre Highlands farm, is situated about 4 miles southwest of Florida
in the tomato area. This farm is used for tomato field research.
addition to the experimentsconducted on Station property, a number of tests
.ied out in groves and on farms of cooperating growers. Close cooperation
.ained also with various bureaus of the United States Department of Agri-
..e and with experiment stations in other states.
At the present time the Station staff consists of three men, two horticul-
.ists and a plant pathologist.
A wide variety of cover and green manure crops have been tested for adapta-
tion to this area. The list includes some 20 species of Crotalaria and over 50
other legumes, including the clovers, vetches, alfalfa, lespedeza, black medic,
soybeans, cowpeas, velvet beans and sesbania, as well as a wide variety of such
non-legumes as teosinte, sorghum, ribbon cane, sudan grass, rye and oats. Thus
far none has proven much better than the common red top or Natal grass for grove
practice on the rockland. Crotalaria spectabilis and Crotalaria usaranoensis have
also done well on this type of soil.
On the marl glades, certain varieties of velvet beans and sesbania have
proven well adapted and the best rates of seeding have been determined. Strangely,
a number of the Crotalarias, particularly spectabilis and striata, have failed to
-row on the marl.
Fertilizer tests with some of these crops have shown a remarkable response
to applications of phosphoric acid, particularly on newly cleared rockland.
S'.aeographedL Report No. 5
Among the windbreak trees under test are Brazilian Oak, Australian Pine,
Bamboo, Eucalyptus, Pongam, Woman's Tongue, Black Olive, Rain Tree, Sapodilla,
Tamarind, Silk Oak, Acacia, native Mahogany, Rhodesian Mahogany, Jambolan,
Lysiloma and Albizzia procera.
The Brazilian Oak and Woman's Tongue have proven better than the others thus
far, chiefly because of their more rapid growth. Albizzia procera has also made
excellent growth. A number of the others, though slower growing, give promise as
windbreaks. These include Black Olive, Tamarind, and Janbolan.
It has been found that Brazilian Oaks set in blasted holes will stand much
more wind, without blowing over, than will similar trees set in shallow, unblasted
A number of ornamentals are now being tested on the Station grounds. The
list includes shade trees, flowering trees and others of promise for foundation
planting. Various lawn grasses are also included. The plantings are now old
enough to indicate typical character of growth, and are attracting much attention
from prospective home owners as well as local residents.
Perhaps the most promising shade tree is Binchofia javonica, introduced from
Southern Asia. It is a rapid growing tree, attractive in appearance and apparently,
well adapted to this area. A new ornamental, the red variety of Bixa orellana
(lipstick tree), is also attracting very favorable attention.
The object of those trials is to test as many species of timber trees as
possible, growing them in ordinary native pine woods, and protecting them from fire.
Of nearly a hundred species tested, the Rhodesian Red Mahogany, Ehay nyasica,
has proven of outstanding interest. It is a native of South Africa, In six years
it has made nearly 3 times the growth of native mahogany, and has proven more
resistant to low temperatures.
Miscellaneous fruit and economic trees
A number of species of plants, thus far of minor importance, have proven
well adapted to South Florida conditions and the Station has been instrumental in
encouraging their wider distribution.
Outstanding among these are: the Ceylon Gooseberry, bearing heavy crops of
purple fruits excellent for jelly; the Muntingia, likewise a heavy bearer of small
red fruits excellent for jellies and preserves; and the Soft Lunbang, a relative
of the tung tree, yielding an oil of properties similar to tung oil.
This Station has cooperated with departments of the Main Station in determining
the chemical analyses of nany subtropical fruits.
Some carefully, conducted spraying tests have brought to light some unexpected
results. Heretofore the failure of mango trees to set good crops of fruit has been
attributed to infections of anthracnose disease. Investigation has brought out
that this failure of fruit set, while undoubtedly influenced to a certain extent
by, disease infection, is influenced even more by other important factors, which
members of the staff are now studying,
A number of new copper fungicides have proven equally, as effective in the
control of anthracnose as bordeaux mixture.
Cold storage tests carried out in cooperation with the cold storage plant at
the Main Station have shown that some varieties of avocado are adapted to cold
storage, and others are not. Different varieties require different temperatures
for best results. A paper describing these experiments was recently given before
the State Horticultural Society meeting at Hollywood.
Fertilizer tests, although handicapped by freezes, storms, and lack of suit-
able experimental groves, have shown worthwhile results. Applications of sulfate
of ammonia intermittent between regular applications of standard mixtures have
proven decidedly worthwhile. The range of tolerance of trees to applications of
certain inorganic sources of nitrogen has been fairly well defined.
Spraying tests have demonstrated excellent control of certain fruit spots
with some of the newer copper fungicides, with less subsequent build up of harmful
scale insects. It has also been shown that weaker concentrations of bordeaux
mixture than those generally used are equal in effectiveness to the stronger
mixtures. These findings, which provide definite financial saving to growers,
were also reported at the State Horticultural Society meeting.
The oil or fat content of 40 or more varieties of avocado has been determined,
and the approximate season of maturity for about 17 of the more common varieties
has been determined by periodic chemical analyses.
A 100-page bulletin, entitled "Avocado Production in Florida", was published
The citrus planting on the Station grounds has progressed to the point where
there are now about 65 different varieties of citrus being tested for adaptation
to this area. The planting includes all of the important varieties of grapefruit,
orange, lime, lemon, tangerine, tangelo, and several varieties of kunquat, lime-
quat, citron, and the like. Many of the more important varieties are being
tested on various rootstocks. Thus far rough lemon rootstock has proven best.
Cleopatra stock shows promise for Persian limes under certain conditions.
Extensive analytical studies with Persian limes have been conducted for in-
formation upon which standard grades could be established. It was found that
top grade fruit from a number of packing houses in the Redland District showed
an average of 50% juice content, by weight.
More recent studies with limes indicate that their keeping quality may be
prolonged considerably by coating then with various wax emulsions.
During the existence of the Station at Homestead, several hundred different
varieties and hybrid selections of tomato have been tested for adaptation to this
area. One new variety, developed in cooperation with the United States Department
of Agriculture, has proven a valuable addition to the small number apparently
adapted to this area. It has been named Glovel, and bulletins describing it have
been published by the Florida Experiment Station and the United States Department
Practically, all of the tomatoes marketed from this section are harvested in
the mature green stage. This stage of maturity is difficult to judge, and all of
the growers realize that some of their fruits are picked too green, and will not
ripen properly. Investigating the percentage of tomatoes which do not ripen
properly, the Station conducted cooperative tests with commercial growers during
the past two seasons and found that a surprisingly high percentage of fruits did
not ripen in salable condition. The average tomatoes picked green ripened only
about 70 percent in salable condition, and ripened irregularly over a period of
several weeks. Tomatoes picked in the turning stage (just beginning to show color)
ripened 95 to 100 percent in salable condition. A number of growers are now ship-
ping turning or pink fruit in 11-lb. baskets at certain seasons of the year.
In an attempt to delay ripening of pink tomatoes, various wax treatments were
used. It was found possible to delay ripening of tomatoes a full seven days with-
out affecting their taste or quality by covering only the buttons with a paste
wax. Efforts are being continued to adapt those methods to commercial use.
Some of the new copper fungicides have proven better than standard bordeaux
mixture for spraying the vines, and have resulted in higher yields.
As a result of five years' tests on the rockland, it was discovered that
doubling the percentage of phosphoric acid in ordinary fertilizer practice more
than paid for the extra fertilizer on new land or on land which had not been
farmed for several years. Where a 4-7-5 formula was about standard, a 4-14-5
was found to be more profitable. Doubling both the phosphoric acid and potash
content of fertilizer decreased the percentage of cracked fruits produced.
In staked tomato trials the Grothen's Red Globe has proven better adapted for
this form of culture than Marglobe, Glovel, Livingstons Globe and Hothouse Globe.
Potato investigations at the Station have dealt with fertilizers, varieties,
rates of planting, and disease control.
Perhaps one of the most outstanding contributions of the Station to the potato
industry has been the discovery for the control of bacterial soft rot, which dis-
ease has caused severe losses to shippers in certain seasons. Carefully controlled
tests have shown that if the tubers are thoroughly dried after washing, the bac-
terial organisms responsible for the rot will be destroyed. As a result of these
experiments, several packing houses have installed equipment costing many thousands
of dollars, and are successfully preventing the losses previously incurred.
Some of the fertilizer investigations have proven of economical value to the
growers. Tests have proven quite conclusively that 100 Ibs. of manganese sulfate
per ton of fertilizer is equal to, if not even better than, the 200 Ibs. formerly
used. Tests have also shown that in most instances 1500 lbs. per acre of ferti-
lizer analyzing about 4-8-5 is more profitable than 2000 Ibs. of the sane mixture,
The muriate form of potash has been found equally as satisfactory as the sulfate
form, and is cheaper. Some of the newer and more soluble forms of nitrogen have
proven satisfactory, and are now being used on a commercial scale by the growers.
Fertilizers analyzing 33 percent of nitrogen from organic sources have proven in
the long run to be nore profitable than those analyzing 50 and 66 percent from the
same expensive sources. On land which has not been fertilized for a number of
years, increasing the phosphate content of the fertilizer front 8 to 12 and even 16
percent has been profitable.
As with tomatoes, some of the new copper fungicides have proven better than the
old bordeaux mixture for spraying potato vines, and have resulted in higher yields.
Tests for control of potato scab have indicated that other factors than soil
reaction are responsible for the occurrence of scab in some of our fields. Seed
treatment tests have shown the hot and cold formaldehyde and the acid mercury dips
to be superior to any of the other standard treatments for our conditions.
Tests with the size and spacing of seed pieces have proven that 28 to 30 bush-
els of seed per acre is a more profitable rate of planting than heavier or lighter
seeding rates. As a result of these tests the growers are planting more seed per
acre than formerly and obtaining more profitable yields. Seed pieces 1 1/2 oz. in
weight, and spaced 9 inches apart in 38-inch rows, have given best results.
Varietal tests have shown thus far that no worthwhile variety seems better
adapted to our narl soils than the red-skinned Bliss Triumph. The new Warba
yields equally as well, or slightly better, but its shape and deep eyes are ob-
jectionable on the market. Of the white skinned varieties, Chippewa has proven
best, and has been planted on a commercial scale by several growers. The old
well-known varieties, such as Spaulding Rose, Irish Cobbler, Early Ohio, Green
Mountain, and Russet Rurals, have proven decidedly unadapted to our conditions
of growth, as have a large number of the newer varieties and seedlings.
Varietal tests with corn have shown most of the sweet corns to be unsuccessful
due to excessive damage from army worms and earworns. Tuxpan and Snowflake, both
roasting ear varieties, are recommended for planting if the ears are to be marketed.
Cuban Flint thus far seems to be best adapted as a field corn.
Of seven varieties of carrot tested, Nantes and Morse's Bunching produced the
best quality roots on the narl.
The new Imperial 847 lettuce has produced solid heads of excellent quality
when grown during the cooler months, and indications are that as the result of
Station preliminary tests, considerable acreage of this crop will be planted in
Dade County next year.
Radishes of the Early Scarlet Globe variety produced well if planted early
before heavy aphis infestation occurred. Bunches packed in ice and shipped by,
boat to New York arrived in excellent condition.
Important work now in progress
More adequate funds appropriated during the last two years have enabled the
work of the Station to be expanded, and several new lines of investigation have been
started, in addition to the expansion which has been possible on the older projects.
Small areas have been planted with selected seedlings of the mango and avocado.
This year for the first time one new mango seedling and 55 new avocado seedlings
are setting fruit. .*. .' '
A project has been started in the breeding and development of the papaya.
A new Persian lime and Valencia orange grove has been planted and will be used for
further fertilizer investigations.
Methods of propagation are being studied with a number of the tropical fruits,
such as litchi, sapodilla, Lecuma and the Annonas, and various rootstocks are
being tested. Preliminary, investigations have indicated good possibilities for
increasing the quality of these fruits by these methods.
The Station's chemical workers are studying various methods of determining
the fat content of avocados, in an effort to secure practical information upon
which maturity standards might be based.
Control of the lime-bark disease is being studied and as the work progresses,
new developments brought to light on the nature of the disease are indicative of
good control possibilities.
Considerable time is being spent on the identification of diseases of a large
number of tropical fruits and ornamentals. Methods of control for many of them
are under investigation.
Attempts to improve the quality of tomatoes shipped from South Florida have
already met with enthusiastic response, and are being continued with good chances
More adequate funds have also helped materially in providing some necessary
equipment for the various experimental enterprises in progress. Field machinery,
and laboratory equipment, both sorely needed, are gradually, being secured as funds
permit, and as a result the work has not only been more productive and more accu-
rate, but less labor has been required for many of the tests.
Visitors and correspondence
A considerable portion of the time of the Station staff is occupied in con-
sultation with visitors and with answering requests for information by mail.
In order to obtain an accurate record of these visitors and of the corre-
spondence, the stenographer was instructed to keep an account, starting October 1,
1938, of all visitors who came to the Station seeking information, and of the
letters which were written in reply to requests for information.
During the period ending April 28, 1939 (seven months), the Station received
547 such visitors. Of these, 251 were residents of the Redland District, 116 were
residents of Miami and immediate vicinity,, 71 were from elsewhere in Florida, 52
were from out of the State, 4 were from foreign countries, and 53 were of addresses
The visitors' inquiries covered the whole range of Station activities, and also
other phases of agriculture and science not covered by the present projects. Chief
among the objects of the visitors was discussion of the experimental results ob-
tained with vegetable crops, citrus, mangos, avocados, and papayas. Another large
group, composed of new residents and prospective home owners, requested general
directions for planting and care of groves. A large number made inquiry for
specific information on the numerous tropical fruits adapted to this area. Many
visitors came to view the Station grounds, which now contain over 500 species of
plants of wide variety,. The reforestation studies have also proven of unexpected
From October 1 through April 28, 205 letters were written in response to re-
quests for information. Of these, 28 came from Miami and vicinity, 7 from the
Redland District, 100 from elsewhere in the State, 60 from out of the State and 10
from foreign countries. The information furnished pertained to fertilizing, spray-
ing, propagating and varietal selecting of tropical fruits, ornamentals and winter
vegetables. Many of the inquiries pertained to papaya culture.