March, 1973 Circular 971
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This guide presents general recommendations for
he production of sweet potatoes in Florida.
modifications may be necessary as improved practices
re developed through research and experience. These
recommendations may vary according to local situa-
ions and growers are urged to consult with their
county extension agent for suggestions and advice in
developing a suitable production program.
Sweet potato weevil regulations have been es-
ablished to control the dissemination of the weevil.
'he entire State of Florida is a regulated area and the
regulations are very specific in terms of what must be
one to satisfy the requirements. Growers should ob-
ain a copy of the regulations from the Division of
'lant Industry, Florida Department of Agriculture
nd follow the recommendations closely.
Georgia Red-Skin "i ....' -,-.1 and 1-.h light
range in color. Good yielder and good plant
producer. Late. Susceptible to fusarium wilt, black
at, and internal cork. Roots slightly variable tapered
Coastal Sweet-Skin copper and flesh orange in
olor. Good yielder and fairly good plant producer.
Centennial-Skin bronze to copper and flesh deep
range in color. Very good yielder, but poor plant
producer. Early. Some resistance to stem rot and in-
ernal cork. Roots variably tapered to cylindrical.
(Cuban Sweet "Boniato" Potato)-Skin dark
ronze and flesh white. Sparse yielder.
The sweet potato requires a long frost-free season
Range of Planting Dates
Area Bedding () Transplanting(2)
North Florida Jan. 15 to Mar. 15 Mar. 1 to June 1
Central Florida Dec. 15 to Feb. 15 Feb. 1 to June 1
South Florida Nov. 1 to Feb. 1 Dec. 15 to June 1
(1) 40 to 50 days are required to obtain first sets (draws)
when soil temperature is maintained at about 80 F.
(2) For early crop, 120 to 140 days are required from this
date to harvest. For late crop, 150 days or more are
required for highest yields.
Sweet potato roots are bedded in special plantbed
structures or bedded in the field for the production of
plants for transplanting. Hotbeds with electric heat-
ing coils or other means of supplying heat to the soil
can be utilized to advantage where cold temperatures
occur during the bedding operation. Where field bed-
ding is used, plastic can be of some advantage as an
over-the-row ground cover until initial emergence of
the shoots. This type of covering must be removed as
soon as the shoots begin to emerge or "burning" of the
shoots will occur. Where permanent or portable
structures are used, adequate ventilation must be
provided to prevent excessive heat and humidity ac-
cumulation and thus reduce the possibility of
developing serious disease problems.
Vine cuttings can be used from the seedbed or
from fields set out for early production. However,
where cuttings are used, a longer growing season is
required before harvest maturity is reached. In some
instances where soil-borne diseases are troublesome,
cuttings can be used to reduce losses. In this method,
plants that appear to be disease-free are selected and
cuttings are taken from them. The cuttings are then
placed directly into the production field. For the
production of an early crop, the use of "draws" taken
from the seedbeds is preferred. Plants can also be
purchased from various sources, if desired, but care
must be taken to assure that they are certified free of
diseases and insects.
Seed Conditioning-Take seed out of cold
storage and keep in 75 to 800 F. temperatures with
high humidity for 2-3 weeks before planting to
Bed Fertilization-For plants grown in struc-
tures. the fertilizer can be broadcast over the ton of
mne son covering tne seed roots. Une pound of a 4-8-8
fertilizer per bushel of seed can be used and watered
in. The application should be repeated after each
pulling of plants. For plants grown in field beds, the
fertilizer can be broadcast and incorporated prior to
formation of the raised bed. An initial application of
800 to 1,000 pounds per acre of 4-8-8 can be used
followed with a sidedressing of 200 pounds per acre of
4-8-8 after each pulling.
Spacing-When using plantbeds, place seed roots
adjacent to one another but not touching. Six to
seven bushels of seedstock of 1 1/2 inch or larger
diameter will furnish plants for 1 acre in three
to bed one
plants for a
en field be
lots 6 inches
:re in this n
nlt 0 tn 15
i apart in tl
lels of seed i
exercised at all phases of production
storage. Residue roots, vines, etc., shot
,from the storage area and the facilities
fungicides or chlorine solutions. Selec
free stock for bedding. Rogue bedded r
to remove diseased plants. Do not use
soil or irrig
e with water
Liu IUIIUvW Cilll U-
oots are required
lis will produce
ion should be
, handling and
uld be removed
is cleaned with
t only disease-
ned from areas
irces of disease
Used, but they
t spores on the
PRODUCTION FIELD FERTILIZATION
The basic or initial application of fertilizer may be
applied before, during, or shortly after transplanting,
or in split applications combining any two or all three
of these. Supplemental fertilizer may be applied
whenever needed during the growing season and es-
pecially after heavy, leaching rains.
Soil pH and Minor Elements-Optimum pH
range for sweet potato production is between 5.5 and
6.0. Minor elements may be needed on certain soils
especially those with pH of 6.0 or above.
Fertilizer Rates and Usage
Soils () Basic Application Applications
Pounds Actual/Acre Pounds Actual/Acr
N P205 KO N P2,0 K2,
Irrigated 60 120 120 10 0 30
irrigated 40 80 80 10 0 30
Rockland 20 40 40 10 20 30
Marl 40 80 80 10 0 30
(1) Sweet Potatoes not recommended on muck and pea
Basic Application-Banded applications (3 to
inches to each side and 3 to 4 inches deep) at the timi
of transplanting or during early stages of growth
subsequent to transplanting have been used witl
success for many years. An alternative method fo:
consideration is the use of split applications whicl
have shown benefit in other crops where high soluble
salts have been a problem. The method involve
placing 1/2 the recommended basic rate of fertilize
banded at the time of transplanting or broadcast prio
to transplanting and the remainder in 1 to 2 applica
tions at later times to the side of the hills. Spli
applications favor reduced soluble salts buildup in thi
root zone and a reduction in the amount of the basi,
fertilizer that may be lost from the root zone due tb
leaching. Timing and number of split application
depend upon weather, the grower's experience, an(
Starter Solutions-In some sweet potato region
outside of Florida, starter solutions are added to the
soil around the plants shortly after they are set in the
field. This application can be helpful in getting the
plants established in the field. The solutions consist o
4 to 6 pounds of a fertilizer such as 10-52-8 in 10O
gallons of water. One-half to one pint of the solution i
applied around each plant in the field.
TRANSPLANTING TO THE FIELD
Exact spacing will be determined by available
equipment and the grower's preference.
Between rows 31 to 5 feet
Between plants 10 to 12 inches
Height of ridges 10 to 14 inches
No. of nlants/acre 9.000 to 12.000
Sweet potatoes are subject to injury from root-
ot, reniform, lesion, spiral, dagger, lance, sting, and
g nematodes. Control measures must be used in
th seedbed and field plantings in areas where
matodes have been a problem.
Nematicides Rates and Usage
ticide usage is subject to changes and cancellations.
!p current on recommendations and regulations by con-
ting county agents, experiment stations, and industry
L row along me
toes for the fall
seedbed will give effective control. Cut one inch above
the soil line.
Scurf (Monilochaetes infuscans)-This disease
involves only the outer layer of the underground part!
of the potato. It does not cause a rot or reduce yield
but causes a dark discoloration of the skin. The dis
coloration may be only a few spots, or may cover mosi
of the surface of the potato. Control: Same as foi
Wilt or Stem Rot (Fusarium oxysporium f
batatas)-The fungus, in the vascular tissue, causes
the plant to wilt, become yellow and stunted and, i:
the attack comes early in the season, the plant ma3
die. The water-conducting tissues of the potato stern
turn dark in color, often making the stem appear blue
from the outside. Affected stems may crack open. This
disease can be carried in or on the seed potatoes and is
able to live for long periods in the soil when once
introduced. Control: Select clean, disease-free pota
toes for seed, rotate fields and plantbeds.
Surface Rot (Fusarium oxysporium)-Th(
fungus produces circular, slightly sunken spots that
are lighter in color than the lesions caused by black
rot. The lesions are quite shallow. Infection takes
place around harvest time and is usually worse in
years when harvesting follows a wet period. During
storage, moisture escapes through the spots and
results in considerable shrinkage and numerous hard
mummified potatoes. Control: Do not harvest when
soil is too wet, avoid injuries to the potatoes, rotate
Soft Rot (Rhizopus spp.)-The fungus causes a
soft, spongy moist decay during the rotting process.
An abundant growth of gray fuzzy mold is usually
produced on the surface. When the rotting process is
completed, or checked, the parts of the affected po-
tato become shrunken, dry and hard. Control: Avoid
injuring potatoes at harvest. Cure and store undei
warm, moist conditions.
Internal Cork (Virus)-Dark spots are produced
within the potato. These spots have no definite pat-
tern in size, number, or location. If the dark area oc-
curs near the surface, its presence may sometimes be
detected by slight indentations, but for the most part,
cutting the potato into thin slices is necessary for de-
tection. Control: Use of internal cork-free potatoes
A limited amount of work has been conducted on
chemical weed control in Florida sweet potatoes.
However, herbicides have and are being tested in the
major sweet potato producing states and neighboring
states as well. There are several herbicides registered
For use on sweet potatoes at the present time. These
herbicides should be used on a trial basis until grower
experience and/or research data can be obtained.
Follow label instructions very carefully.
Herbicides Rates and Usage
Time of Lbs./Acre
Herbicide to Crop Ingredient) Remarks
DCPA Pre- 10.5 Broadcast soil
(Dacthal) transplant application at
time of trans-
vernolate Pre- 1.5 to 2 Needs to be soil
(Vernam) transplant incorporated.
Rate depends on
type of bed
diphenamid Post- 4 Apply overtop
(Dymid) transplant immediately
(Enide) after trans-
planting. Do not
areas to crops
not on the label
within 6 months
DCPA Post- 10.5 Broadcast soil
(Dacthal) transplant application at
time of last cul-
up to 6 weeks
Sweet potatoes may be harvested anytime after
the roots exhibit satisfactory size and yield. The roots
can be harvested by using a "middlebuster" to expose
the roots for pick up or by using a sweet potato
harvester which is similar in operation principle to the
Trish notfto harvester. Whichever method is utilized.
some method of cutting the vines is best used prior to
the digging. With the "middlebuster," the vines can be
cut by utilizing two coulter discs placed 18 inches
apart in front of the middlebuster. Care should be
exercised to insure that the depth of the discs is ad-
justed so as not to injure or cut the roots. When
utilizing the sweet potato "digger," a slightly different
approach is often used. The coulter discs are spaced to
conform with the width of the bed or hill. Following
the discs, a flailing-type beater or a spinning blade
mower is used to remove most of the foliage and vines
from the row. This allows only the roots to be handled
over the digger, preventing handling problems caused
by excessive accumulation of 'ines and leaves.
CURING AND STORAGE
Sweet potatoes are marketed as "uncured" or
"cured" roots. Most early potatoes are marketed
shortly after they are dug without curing or have only
a brief curing period to "set" the skin. "Cured" roots
most frequently are stored and sold at a later date.
Curing facilitates the formation of wound-cork layers
beneath injured areas on the root. Some wounding
occurs during the harvesting process regardless of how
carefully they are handled. However, careful handling
reduces the amount of injury and reduces the poten-
tial for loss due to shriveling, storage rots, etc.
The curing conditions should be 4 to 7 days at 80
to 850 F. with a relative humidity of 85 to 90 percent.
Following proper curing, storage conditions should
be: 55 to 600 F. and a relative humidity of 85 to 90
percent. Storage below 550 should be avoided because
chilling injury may result.
1. Florida Department of Agriculture, Division of Plant Industry,
"Florida Sweet Potato Weevil Regulations."
2. Florida Extension Circular 193, "Commercial Vegetable Insect
and Disease Control Guide."
3. Florida Extension Circular 196, "Chemical Weed Control for
Florida Vegetable Crops."
4. Florida Extension Circular 225, "Commercial Vegetahie Fer-
5. USDA Agriculture Handbook 388, "Sweet Potato Culture and
6. USDA Farmers Bulletin 1059, "Sweet Potato Diseases."
7. USDA Pamphlet 874, "The Sweet Potato Weevil."
Since extension circulars are revised from time to time, be sure
I Lraue names in mns puloncaion
signify that they are recommended to the exclusion of other
of suitable composition.
Prepared by: Stephen R. Kostewicz and James Montelaro wit]
cooperation with other personnel of the Institute of Food ani
Agricultural Sciences. Special assistance was given by Mr. J. E
Brogdon, Dr. D. W. Dickson, Dr. R. S. Mullin and Dr. W. L
AY 2 8 97 MAY 9iga76.
This public document was promulgated at an an-
nual cost of $393.96, or 3.94 cents per copy to inform
potato growers how to grow sweet potatoes.
COOPERATIVE EXTENSION WORK IN AGRICULTM E AND HOME ECONOMICS
(Acts of May 8 and June 30, 1 4)
Cooperative Etension Service, IFAS, U tity of Florida
and United States Department of Agriclte, Cooperating
Jo N; Busby, Dean