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Copyright 2005, Board of Trustees, University
Growing Sweet Potatoes for Profit
.R. D. William, N. J. Tielkemeier, and L. H. Halsey
Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ John T. Woeste, Dean L S B
FIELD PREPARATION AND PLANTING
Growing top quality sweet potatoes begins with
planning several months before you plant. Read
Part I: PLANNING AND LIMING before you pre-
pare the soil or buy your plants. Select your field
carefully, test your soil, and add lime at least 2
months before planting. After completing these
steps, you are ready to prepare the field and plant.
Sweet potatoes must be free of bruises, cracks,
diseases and insects to be sold for a profit. Mis-
takes made at planting time can not be corrected
later. Start your field production by following the
steps in this publication.
PREPARE THE SOIL
Sweet potatoes grow best when you plow the
soil at least 6 weeks before planting. Plowing early
helps to rot old plants and weeds. You also can
apply lime more evenly to plowed soil than to a
field full of weeds. After you plow and lime, disc
or till the field once or twice before planting to
loosen the soil and kill weeds.
Nematodes are tiny worms that live in the soil.
They harm the roots of many plants. Nematodes
must be controlled because they reduce yields and
destroy root quality.
Sometimes you can see what nematodes do to
plants. Look carefully at the roots of several kinds
of plants when they are growing. Roots that look
knotted will contain root-knot nematode. Other
kinds of nematodes may only sting or make a hole
in the root. Usually this kind of nematode leaves
a scar on the root. Sometimes nematodes will
cause sweet potato roots to crack open as the root
grows. In bad cases, roots may never grow. Sweet
potato vines may look yellow and stunted because
the roots cannot take up enough water and ferti-
If you think nematodes may live in your soil,
you can have your soil tested in this way:
Take about 10 small samples of soil from
your field in late summer or early fall the year be-
fore you want to plant sweet potatoes. Try to take
a few live roots and some soil near these roots.
Mix these soil samples together in a clean
pail. Fill a clean plastic bag with part of this
mixed soil. Be careful to keep the sample cool.
Take it to your County Agent as soon as pos-
sible. Ask your County Agent to have the soil
tested for nematodes.
In several weeks, you will receive a report. If
nematodes are present in your soil, they will be
listed by name.
Now you can select the right control method.
Nematode problems in your soil may be reduced
if you plan ahead. Rotate your crops so that sweet
potatoes follow corn, small grains or sod pastures.
The nematodes that harm most vegetables do not
multiply as fast when these crops grow in the field
before sweet potatoes.
Just before planting, nematodes can be con-
trolled by using chemicals that kill these pests.
These chemicals are called nematicides. You can
buy either liquid or solid (granular) types of nema-
ticides. The liquid or fumigant types of nematicides
form a gas in the soil. This gas moves through the
soil to kill the nematodes. To keep the gas from
escaping you must seal the soil surface. Thor-
oughly wet the soil surface with water or press it
with a roller. Special equipment that costs about
$100 to $150 is needed to apply fumigant nema-
Growers who have the equipment inject the liquid
nematicide into the bed using a gravity-flow appli-
cator and chisels or blades.
Solid or granular nematicides can be applied
with simple equipment. Mix the nematicide evenly
into the soil so that it will dissolve in the soil
water. Nematodes are killed when they come in
contact with the chemical. Granular nematicides
can be applied with a broadcast type of insecticide
spreader. Small farmers can follow the instructions
given below the photo.
Small farmers who do not have a tractor may
apply solid nematicides such as granular Dasanit
15G using a lawn fertilizer or pesticide applicator.
Be sure to measure and apply the exact amount of
chemical into the soil right after application. Do
not touch the chemical. Wash your skin and
clothes when finished. These chemicals are poisons
and can injure or kill people. With careful nema-
ticide use, you can grow top quality sweet potatoes
even though nematodes may live in your soil.
The following chart lists some nematicides that
can be used for sweet potatoes. Before you apply
these nematicides, destroy all live roots that may
have nematodes. Let the plant root rot and decay
completely. Then, apply the nematicides 2 to 3
weeks before planting sweet potatoes. If you use
liquid nematicides, till the soil about 1 week after
you applied the chemical. This will help the chem-
ical escape from the soil. With normal tempera-
tures, you can plant sweet potatoes about one week
after you till or two weeks after you apply the
nematicide. But if it is cold, wait another week
before planting. Be sure to mark the row where the
nematicide was applied. Now you can fertilize and
plant in the same treated area.
AMOUNT AND TYPE OF NEMATICIDE
Type of application equipment
One chisel per row Two or more chisels per row
Fumigant nematicides (Amount in fluid ounces per chisel per 1000 ft of row)
D-D 60 to 75 80 to 100
Telone II 35 to 45 45 to 60
Soilbrom -85 or
Dowfume W85 12 to 18 12 to 18
feet of row
Solid or granular (12 to 15 Pounds per row
nematicides inches wide) (broadcast)
Mocap 10G 2.5 to 3.3 60 to 80
Dasanit 15G (not recommended) 20 to 46
The best way to grow top quality sweet potatoes
to keep the pests out of your fields. To be safe,
jy and plant "certified" plants for your first plant-
ing date. These "certified" plants are checked by
plant inspectors from the State Department of Agri-
culture to be free of sweet potato pests. "Certi-
:-1" plants may cost more, but later problems and
the chance of losing your whole crop are less.
Read the certificate carefully before you buy.
The tag or certificate will list the state agency that
checked or inspected the plants. It also will certify
that the plants are free of the pests on the certifi-
Be sure to save the certification bands that hold
the bundle of plants together. If there is any prob-
lem with your plants, the Florida Plant Inspectors
will need the bands to check on the certification
Be careful to control any sweet potato pests that
may be in your field before you plant these "certi-
fied" plants. If you don't, these plants will become
infected from pests in your field and your money
will be lost.
PLANT IN FIELD
Sweet potatoes should be planted on ridges or
beds. Too much rain can kill sweet potato roots.
The ridges help drain the water from the field.
Also, digging the potatoes is easier when they are
grown on ridges. Note the following information
-about distances between rows and plants and the
number of plants needed for an acre.
Distance between: rows 3/2 to 5 feet
plants in row 10 to 12 inches
Height of ridges 10 to 14 inches
(Rockland soils) with gentle slope
(3 to 4 inches)
Number of plants
per acre 9,000 to 12,000
" .- ,
Be sure to form the ridges over the treated area
if you applied a nematicide or banded your ferti-
lizer in wide bands.
"Certified" sweet potato plants can be planted
early to produce an early harvest. Later plantings
can be made using vine cuttings from the first
field planting. You should cut vine tips with 4 to
5 large leaves. Carefully select vine cuttings that
appear completely free of disease and insects.
Plant directly into the production field. Allow
extra time for roots to form and grow when vine
cuttings are planted.
Select vine cuttings having 4 to 5 large leaves.
Be sure the vine cuttings appear absolutely free
of disease and insects before planting in the
Two cups of water should be poured over each
sweet potato plant to make the soil firm and get
the plant started. You can mix 4 to 6 Ibs. of a
starter fertilizer such as 10-52-8 in 100 gallons of
water and apply it near each plant at transplanting.
Use only starter fertilizers that dissolve completely
Good quality sweet potatoes of the right variety
can be sold for profit.
Red Jewel is now the leading variety in Georgia
and Florida. The skin is red, but it can scuff easily.
Root flesh is orange and has low fiber content.
Yields are average, but storage and shelf-life qual-
ities are only moderate. It produces an average
number of plants from seed roots.
This variety has some resistance to peanut root-
knot nematode and stem rot disease. The variety
cannot be grown in fields with southern root-knot
nematode unless you control the pest.
Jewel is similar to Red Jewel, except the skin
is tan to buff color. It resists southern root-knot
and sweet potato flea beetles.
Centennial variety has a bronze to copper color
skin. Root flesh is deep orange. Yields are excel-
lent and early (90-120 days). Produces few plants
from seed roots. Roots are tapered to cylindrical.
This variety has some resistance to wilt or stem
rot, internal cork and peanut root-knot nematode.
But it should not be planted where southern root-
knot nematode is known to infest the field. Moder-
ately resistant to sweet potato flea beetles.
Georgia Jet has a light red skin. Roots are
orange and have good internal quality. Yields are
excellent and early (90-100 days). Requires irri-
gation water to keep an even or uniform soil mois-
ture to reduce root cracking. This variety should
not be planted in fields infested with wilt or stem
Georgia Red has a coppery-red skin. Root flesh
is light orange. Yields are good, but late. Produces
many plants from seed roots. Root sizes and
shapes vary and sometimes are poorly shaped.
Stores well with long shelf life.
The variety cannot be grown where wilt or stem
rot, black rot, and internal cork diseases are know
to infest the field. It is resistant to peanut root-kr
nematode and partly resistant to southern root-knc
Carver is a new variety with a deep rose si
The root flesh is dark orange. Yields are avera.
with good canning and baking qualities.
It can be planted in land infested with wilt o-
stem rot and southern root-knot nematode. T;
planting a few rows on a trial basis to learn mor
about the variety.
Boniato Types. In Dade County several types
boniato sweet potatoes are grown. Skin is reddish
purple. The flesh is white with a starchy texture r
consistency. Yields are variable. It is planted fro
BUY CERTIFIED PLANTS
Sweet potato plants that show any sign of a pest
should never be planted in your field. If you grow.
your own plants or buy them from a neighbor, b
sure they are free of nematode, disease and inse-
pests. A mistake at planting time can never be cor
CERTIFIED BY STATE
TO BE FREE OF:
FERTILIZE THE SOIL
In Part I, of this guide you learned about soil
testing. Your County Agent sent you the "Soil Test
f, Results" with a fertilizer recommendation. Follow
l~of your agent's recommendation and learn about fer-
Stilizing sweet potatoes by reading this section care-
nb A complete fertilizer is recommended for sweet
0) potatoes in Florida. Complete fertilizers contain
nitrogen (N), phosphorus (P205), and potassium
1 (K20). For most root crops, a fertilizer with one
r part nitrogen, two parts phosphorus, and two parts
a: potassium is best. This gives an N-P-K ratio of
Ic A total amount of each fertilizer nutrient is given
-r in the fertilizer analysis. A good fertilizer for sweet
t. potatoes contains a 4-8-8 or a 6-12-12 analysis.
m The 4-8-8 analysis fertilizer is 4 percent nitrogen,
8 percent phosphorus, and 8 percent potassium.
In other words, every 100 Ibs. of fertilizer contains
4 Ibs. of nitrogen and 8 Ibs. each of phosphorus
When you apply 1000 Ibs of 4-8-8 fertilizer per
acre, you are really applying 40 Ibs of nitrogen,
80 Ibs of phosphorus and 80 Ibs of potassium per
acre. This is a good recommendation for sweet
potatoes growing without irrigation water. When
you can water the potatoes, use the 6-12-12
analysis fertilizer for higher yields.
PER O1 1ER
Apply 1000 to 1200
Ibs per acre
Apply the 4-8-8 to sandy, sandy loam or marl
(Dade County) soils without irrigation.
Apply the 6-12-12 to sandy, sandy loam or rock-
land (Dade County) soil with irrigation.
The safest way to apply the fertilizer is to spread
or broadcast about half of the fertilizer evenly over
the field before planting. Mix the fertilizer into the
soil. Careful placement of the exact amount of
fertilizer is necessary or the fertilizer may "burn"
your plants. High amounts of fertilizer placed too
close to the roots can injure the sweet potatoes.
The fertilizer also may be spread in a band
about 2 feet wide and mixed into the soil before
planting. Remember to place the fertilizer directly
over the nematicide treated area. The rest of the
fertilizer will be applied or side-dressed about 3
to 6 weeks after planting. (See Part III about side-
Select your sweet potato varieties carefully.
Each variety has different eating qualities and
growing needs. You should learn about the needs
of your variety. You also should know which pests
live in your field. Then, you can choose a variety
that is resistant to these pests.
Be sure to select a variety that you will be able
to sell. Ask your buyer or customers which variety
they want to buy.
READ: 1. Florida Extension Circular 440,
"Growing Sweet Potatoes for Profit".
PART I Planning and Liming
PART III Field Production and
PART IV Harvesting and Marketing
2. Florida Extension Circular 225, "Com-
mercial Vegetable Fertilization Guide".
3. Florida Vegetable Crops Department
Research Report VC3-76, "Seasonal
Response of Vegetable Crops for
Selected Cultivars in North Florida,
II. Okra, Sweet Corn, Sweet Potato".
4. USDA Agricultural Handbook 388,
"Sweet Potato Culture and Diseases".
Because Extension circulars are revised periodi-
cally, be sure to obtain the latest copy.
Acknowledgements: The authors thank the many
staff and faculty members of the Institute of Food
and Agricultural Sciences (IFAS) including J. M.
Nehiley, P. F. Korsching, L. Carter, J. A. B. Pierce,
L. T. Christenberry, J. R. Yelvington and W. S.
Cheshire for helping develop and evaluate this
production guide. Special contributions were made
R. A. Dunn Nematode Control
We also acknowledge the support from the IFAS
Center for Rural Development Programs.
The use of trade names in this publication is
solely for the purpose of providing specific infor-
mation. It is not a guarantee or warranty of the
products named and does not signify recommenda-
tion of the product to the exclusion of others of
This publication was promulgated at a cost of
$214.20, or 7.1 cents per copy, to provide new
information on growing sweet potatoes to both
large and small producers.
Single copies are free to residents of Florida and may be ob-
tained from the County Extension Office. Bulk rates are
available upon request. Please submit details of the request to
C. M. Hinton, Publication Distribution Center, IFAS Building
664, University of Florida, Galnesville, Florida 32611.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
K. R. Tefertiller, Director