Front Cover
 Plant growing
 Select and prepare the soil
 Care of the crop

Title: Growing sweet potatoes
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00084400/00001
 Material Information
Title: Growing sweet potatoes
Series Title: Growing sweet potatoes
Alternate Title: Circular 160 ; Florida Agricultural Extension Service
Physical Description: Book
Language: English
Creator: Norton, Joseph D.
Nettles, V. F.
Publisher: Agricultural Extension Service, University of Florida
 Record Information
Bibliographic ID: UF00084400
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 221275113

Table of Contents
    Front Cover
        Page 1
        Page 2
    Plant growing
        Page 3
        Page 4
        Page 5
    Select and prepare the soil
        Page 6
        Page 7
        Page 8
    Care of the crop
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
Full Text

Circular 160 Vegetable Garden Series

(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida,
Florida State University and United States Department of Agriculture, Cooperating
M. O. Watkins, Director

Growing Sweet Potatoes

Assistant Vegetable Crop Specialist
Associate Horticulturist, Agricultural Experiment Station
(Prepared in cooperation with workers of Florida Agricultural Experiment
Station and Florida Agricultural Extension Service)

Fig. 1.-These 4-H Club boys have a good crop of sweet potatoes.
AWAt =

This publication contains some current recommendations for
sweet potato production in Florida. It is intended for use pri-
marily by 4-H members and other home and market gardeners
who grow sweet potatoes. However, the commercial grower may
find the recommendations equally applicable to his farming op-
eration. The Sweet Potato Production Guide, Circular 97B,
also contains other useful information on the crop.
Florida farmers have grown sweet potatoes for many years.
Potatoes may be harvested here from late spring until late fall.
Early potatoes, usually sold from June to August, sell for a
higher price. Although the price received from the sale of the
main crop is usually lower, farmers may find it profitable to
store theirs until the price rises during the winter months.
Sweet potato growers may have problems-insect, disease
and other. Successful production depends on many things.

Fig. 2.-Unit No. 1 or copper-skinned Porto Rico sweet potatoes.

However, following recommendations in this publication should
solve many of the common problems.

Varieties.-Unit No. 1 or Copper-Skinned Porto Rico is a
standard vining type. It is copper skinned with light salmon
color flesh. You may know this potato by other names. Gold-
rush, another good variety, has copper skin and bright flesh. It
is wilt-resistant.
Seed and Plants.-Use only certified sweet potatoes or plants
known to be free of disease. Throw away ones that have rotten
spots, bruises or discolored ends. It is a good idea to cut some
with a knife to see if they are diseased. Plant only strong plants
that are free from disease. Look at your potatoes or plants care-
fully before using either.
In growing seed for the next year, take vine cuttings. Plant
them on land.where sweet potatoes have not been grown before.

Fig. 3.-Goldrush sweet potatoes.

The seed from the vine cuttings should be free from disease.
Select seed potatoes from hills with the most No. 1 potatoes.
To control sweet potato weevils, dust seed potatoes with 10
percent DDT before placing them in storage. Use 1 pound for
8 bushels or 1/2 cup per bushel. In addition, dust bank or stor-
age house with 10 percent DDT. CAUTION: IF TREATED

Fig. 4.-Examining potatoes for internal diseases, particularly
internal cork.

Seed Treatment.-Use one of the two treatments below be-
fore bedding potatoes:
1. Mix 1 pound of Semesan Bel in 8 gallons of water. Dip
potatoes for 1 minute. Do not soak. Either an open mesh sack
or bushel crate may be used to hold potatoes. A metal drum
may be used for the dipping solution. Let potatoes drain and
then bed them quickly.

2. Mix 1 ounce of mercuric chloride in 1/ gallon of hot
water. Add this to 71/ gallons of cold water. Use a clean
wooden container for the dipping solution. Dip for 8 to 10 min-
utes and bed.
Caution.-Semesan Bel and mercuric chloride are poisonous.
Do not eat or allow animals to eat treated potatoes. When you
have finished treating the potatoes, pour the solution into a
hole and cover with soil.
Plant Bed.-Make the plant bed where sweet potatoes have
never been planted or bedded before. The bed should be on high-
er ground than where sweet potatoes have been before. Any soil
that is used on the bed should also come from clean land. Good
soil can become diseased by drainage water from diseased land.
Woods dirt from a ridge that does not receive drainage water
is best. Never use sand from a ditch or creek. If you use an
old sweet potato bed, remove soil to a depth of 12 inches. Drench
with a formaldehyde solution (mix 1 pint of formaldehyde in 15
gallons of water). Refill the bed with new soil. Then drench the
bed and place potatoes in bed as close as possible without touch-
ing. Use potatoes 11/2 inches in diameter or larger. Handle them
carefully to prevent bruising. Allow 12 square feet per bushel.
Six to seven bushels furnish plants for one acre at three pulling.
Cover potatoes with two inches of soil. If early plants are
needed, it is best to use a fire or electric-heated hotbed. Do not

Fig. 5.-Sweet potatoes placed adjacent to each other without touching.

use manure to heat the plant bed. Manure may have potato dis-
eases in it.
Water often enough to keep the soil around the potatoes
moist but not wet. Heated beds need more water.
Maintain the soil temperature at 80 to 850 Fahrenheit. Place
a thermometer in the hotbed soil. If an electric bed is used,
set the thermostat at 80 to 85 degrees.
For details on construction and operation of plant beds, you
should request Extension Circular 120, Electric Hotbeds for
Sweet Potatoes, from your County Agricultural or Home Dem-
onstration Agent.
Field Bedding.-If you are bedding sweet potatoes in the field,
plant them 6 inches apart in rows 31/2 to 4 feet wide. This will
require 35 yards of row space for a bushel of potatoes. Eight
to 10 bushels should provide plants for an acre in three pulling.
Vine Cuttings.-Vine cuttings 12 to 15 inches long from early
planted sweet potatoes will produce good late potatoes, usually
free of disease. One acre of potatoes will produce vine cuttings
for 10 to 15 acres.
Sweet Potato Weevil Control in Plant Beds.-Use certified
or weevil-free seed. If home-grown seed are used, dust seed
with 10% DDT dust before bedding. Use 1 pound for 8 bushels
or 1/2 cup per bushel.
Also apply 2% dieldrin dust, 1/ pound to 80 square feet
of bed or to each 100 feet of row bed. Make the first applica-
tion when first plants begin to show color in stems. Apply on
and around base of plants. Make second application when all
plants are up. Cover all plants and soil around them. Make
additional applications after each pulling.
Heptachlor 21/2% dust may be used in place of dieldrin for
second and subsequent applications.

Soil.-Choose a loose soil that is well drained. Do not use
wet soil. If you must use sod land, choose a plot where a good
crop of grass grew the year before.
Plant potatoes on land where they have not been grown be-
fore. If you do not have new land, plant them on soil where
they have not been grown for the last five years. Do not plant
on land where water has drained from soil where sweet potatoes
have been grown.

Liming and pH.-Apply lime to sweeten the soil-but only
after a reliable soil test indicates a need for it. Adjust the pH
(relative acidity) of acid soils to 5.5 to 6.0 by adding lime. Two
hundred to 300 pounds of finely ground dolomitic lime per 1/4
acre usually will be enough except on extremely acid soils.
Plowing.-Turn the soil 6 to 8 inches deep. Do not plow
when the ground is wet. Prepare the soil at least three weeks
before planting.
Make beds or ridges 10 to 14 inches high with a turnplow.
Drag the tops of the beds off just before planting. Then you
will transplant into moist soil.

Planting Dates
Set Draws
Area Bed Seed or Vine Cuttings
North Florida Feb. 15 to April 15 April 1 to June 1
Central Florida Jan. 15 to April 15 March 1 to June 1
South Florida Oct. 1 to April 15 Nov. 15 to May 15

Early potatoes usually bring a higher price. For example,
the five-year (1952-1956) average price paid for 100 pounds of
sweet potatoes during July was $7.06. The average price paid
during October of this same period was $5.68.
Planting Distances
Plants Required
Spacing Ridges for 1/4 Acre
Between plants: Height: 2,500 to 3,000
12 to 14 inches 10 to 14 inches (70 to 80 plants weigh
Between rows: Width: 1 pound)
3% to 4 feet 24 to 30 inches

Transplanting.-Use average size plants (about 12 inches
long) for transplanting. Certified or disease-free plants may
grow best. Vine cuttings may be taken from early planted field
and set for a later or main crop. Set plans or vine cuttings
4 to 6 inches deep.
Transplant when conditions are best soon after a rain,
when cloudy, or in late afternoon. Dip roots in soft mud or
water when setting. If the weather is dry, the plants must have
water. Pour about 1 pint of water (starter solution) around
each plant. Make the starter solution by mixing 2 pounds of
6-8-6 fertilizer in 50 gallons of water or 2 tablespoons in 1 gallon.

Replant within three or four days. A good stand means a
higher yield.

Fig. 6.-Set plants on ridges 10 to 14 inches high and 24 to 30 inches wide.

You may broadcast the fertilizer over the soil before making
the ridges. Band placement at or after planting is best. Place
each band 2 to 3 inches below and 3 to 4 inches to the side of
the planting row.
If you band the fertilizer, use half of it one week after plant-
ing. Apply the other half three to four weeks later.
Use fertilizer as recommended below:

Pounds for
Soil Type Fertilizer Grade 4 Acre

Marl 4-8-8 175
Light sandy 4-8-8 250
Dark sandy 4-8-8 200

Early market sweet potatoes may receive double the amount
listed above.
Top-dress only after periods of heavy rains. Use 25 pounds
of nitrate of soda and 6 pounds of muriate of potash on 1/ acre.
Equivalent rates of other forms of nitrogen and potash can be
used. Over-fertilization of sweet potatoes may result in poor
yield and quality.
Minor Elements.-Marl soils and sands with a pH above 6.0
may need manganese. Mix 1/ pound of manganese sulfate in 121/2
gallons of water and spray on 1/4 acre of potatoes. Two table-
spoons per gallon may be used for 100 feet of row.
Soil with a pH of 7.0 or higher may require boron. Apply
4 pounds of common borax to 1/4 acre of potatoes before plant-
ing. Use boron only when a known deficiency exists.


Plow or hoe often enough to control weeds and grass. Use
cultivating equipment that will maintain a high ridge. Two or
three plowings usually will be enough.
Sweet Potato Weevil Control in the Field.-Apply 2% diel-
drin or 21/2% heptachlor dust (nongranular) in 6- to 8-inch strips
along the row. Direct the dust at the base of plant at ground
level. Be sure to dust under the leaves. The number of times
you dust depends on the variety you grow.
For Unit No. 1 or Copper-Skinned Porto Rico and other deep-
rooted varieties, dust 20 pounds of dieldrin on 1/4 acre when
largest roots are 1/2 to 1 inch in diameter and vines are meeting
in the middles.
For Goldrush and other shallow-rooted varieties, dust 10
pounds on 1/4 acre when largest roots are 1/2 to 1 inch in diameter
and make a second application about two weeks later or when
ground cracking becomes common.
Caution.-Dieldrin and heptachlor are poisons. Do not apply
within 30 days of harvest.
Insect Control.-Watch for the first signs of insect injury.

Apply the dusts or

sprays listed below.




Spray: (Amt. in 25 gal.

Gold bugs



Armyworm and
Potato hornworm

5% DDT

5% Chlordane,
10% Toxaphene

5% DDT,
5% Chlordane,
10% Toxaphene

5% DDT, 10% Toxa-

DDT wettable powder,
% lb., 50%

Toxaphene wettable
powder, 40%, % lb.
DDT wettable powder,
50%, 1/2 lb.

Toxaphene wettable
powder, 40%, % lb.
DDT wettable powder,
50%, % lb.

Toxaphene wettable
powder, 40%, % lb.
DDT wettable powder,
50%, 1/2 lb.

Sweet potato weevil

White-fringed beetle

See "Sweet Potato Weevil", Pages 4, 6 and 9.

Field control program for sweet potato weevil
should give control, or dust with 5% DDT.

Caution.-Above insecticides are poisonous. Apply only as
Harvest sweet potatoes when the yield of U. S. No. 1 potatoes
will be highest. It usually takes a 140 to 150-day growing sea-
son. You may harvest a profitable yield of early potatoes in
120 days.
Dig around a few hills in the patch. If most of the potatoes
are 13 to 33/ inches in diameter, it is time to harvest.
Plowing Up Potatoes.-A middleburster with slat wings is
the best plow to use. Any large middleburster will do a good job.
Do not use a turnplow. It will cause more cutting and bruising
than the middleburster. The home gardener may harvest a
small amount with a spading fork.
Vines may slow the plowing operation, and it may be neces-
sary to remove the vines or place a vine-cutting attachment on
the plow. Install a special vine-cutting attachment on the mid-
dleburster. Rolling coulters have been used for cutting vines.
Set one coulter on each side of row (about 18 inches apart) and
shallow enough not to cut potatoes.
Caution.-Set vine cutter so no potatoes will be injured.
Harvesting Care.-When harvesting sweet potatoes remem-
ber to:
1. Pick up potatoes close behind the plow. One-half hour
of bright sunshine will sunscald tender potatoes.
2. Handle potatoes carefully. Bruised potatoes do not keep
well and are discolored around bruised spots. Handle as you
would an egg.

Fig. 7.-Potatoes harvested too late. Center potato is U. S. No. 1 size.
Those on both sides are culls of jumbo size.

Fig. 8.-A middleburster is used for plowing up potatoes.

Fig. 9.-Rolling coulters are used to cut potato vines.

3. Cover field containers with vines or take them to the
4. Pack potatoes in the field, if possible, in bushel baskets,
wire-bound crates or sweet potato crates. Do not put the po-
tatoes in sacks for handling.
Grading.-Grade your potatoes by U. S. standards. The four
grades are: U. S. Extra No. 1, U. S. No. 1, U. S. Commercial
and U. S. No. 2. The most practicable grades to pack are U. S.
No. 1 and U. S. No. 2. The U. S. standards for these grades are
given below. Grade carefully so your potatoes will meet the
grade requirements.
U. S. No. 1
U. S. No. 1 potatoes are of one type (variety). They are also
firm, fairly smooth, fairly clean and not more than slightly mis-
shapen. They must be free from freezing injury, internal break-
down, black rot and other decay or wet breakdown except soil
rot. Potatoes are free from damage caused by secondary root-
lets, sprouts, cuts, bruises, scars, growth cracks. They are free
from damage caused by scurf, soil rot or other diseases, wire-
worms, weevils or other insects, mechanical or other means.
Size.-Use a grading card to check potatoes for size. A
grading card may be made from plywood or cardboard. Figure
11 shows you how to make a card for the U. S. No. 1 grade.
Each potato shall be not less than 13/ inches wide and 3
inches long nor more than 33/ inches wide and 10 inches long.
(See number off-size.) Each potato must weigh no more than
20 ounces.
Amount of Defects Allowed.-Certain defects may not be
found during handling and grading. A total of not more than
10 percent, by weight, may fail to meet the requirements of this
grade. Not more than 5 percent may be due to defects causing
serious damage. No more than 2 percent may be affected by
soft rot or wet breakdown except soil rot.

U. S. No. 2
Potatoes are firm and of one type (variety). They must be
free from freezing injury, internal breakdown, black rot and
other decay or wet breakdown except soil rot. Potatoes are free
from serious damage caused by dirt or other foreign matter,
cuts, bruises, scars and growth cracks. They must also be free
from serious damage caused by soil rot or other diseases, wire-
worms, weevils or other insects, mechanical or other means.

Size.-Each potato shall be not less than 11/2 inches in diame-
ter and shall weigh not more than 36 ounces (21/4 pounds). (See
amount of off-size allowed.)
Amount of Defects Allowed.-Not more than 10 percent, by
weight, may fail to meet the requirements. Not more than 2
percent may be affected by soft rot or wet breakdown except
soil rot.
Amount of Off-Size Allowed.-Not more than 10 percent, by
weight, may not meet the size requirements. Not more than 5
percent may be smaller or shorter than the minimum require-
Package.-Three containers may be used for your potatoes.
Use the one-bushel basket, wire-bound crate, or sweet potato
Weights.-One bushel of sweet potatoes weighs 55 pounds
when green (at harvest) and 50 pounds when cured.
Pack.-Always give the right weight. Have just as good po-
tatoes in the bottom of container as you have on top. Then,
selling at a good price will be an easy job.

Curing.-Store only good, sound sweet potatoes. Cure at 85
degrees for 7 to 10 days. Have a high relative humidity of 85

Fig. 10.-Left to right: U. S. No. 1, U. S. No. 2 and cull potatoes.

percent. A high relative humidity means there is a lot of mois-
ture in the storage house. After the curing period is over,
store at 55 degrees and a relative humidity of 85 percent. Tem-
peratures above 60 degrees may cause sprouting and tempera-
tures below 50 degrees may cause chilling. A low relative hu-
midity will cause heavy shrinking.
Houses.-A sweet potato house is best. Many tobacco barns
are used for storage. Tightly built barns may be used for stor-
age. Allow 21/2 cubic feet per bushel. A barn 16 by 16 feet of
average height will hold 1,000 bushels.
Place packed crates or baskets in storage house. Stack U. S.
No. 1's and U. S. No. 2's in different sections of the house. Allow
a walkway between. Then you can remove either grade without
touching the other.
When any lot is handled in the potato house, sell all of this
lot as soon as possible. You may lose them by spoilage if they
are left in the house.
For further information on storage of sweet potatoes, re-
fer to:
Storage of Sweet Potatoes, USDA Farmers Bulletin 1442.
Utilization of Flue-Heated Tobacco Barns for Sweet Potato
Storage, USDA Farmers Bulletin 1267.
Insect Control in Storage.-Place only weevil-free potatoes in
storage. Clean up and empty the storage house or bank at least
one month before the new crop is planted. Burn all infested
potatoes. Dust the storage place as soon as it is empty. Use 1
pound of 10 percent DDT for each 1,600 square feet of surface.
Disease Control in Storage.-Clean house thoroughly before
placing potatoes in storage. Spray floor and walls with a solu-
tion of 1 part of 36% formalydehyde to 30 parts of water. Place
only disease-free potatoes in the storage house. The curing proc-
ess given above will greatly reduce soft rot, Java black rot and
surface rot.

You may sell your potatoes:
1. Green-soon after digging.
2. Cured-after 7 to 10 day curing period.
Most early potatoes are sold green. Cured ones may be held
until the price is high.
Buyers prefer sweet potatoes that have been washed and
some prefer them waxed. If washing and waxing equipment is

Fig. 11.-A grading card for U. S. No. 1 potatoes.

available, use it, as it will pay. Caution: Wash and wax at sell-
ing time. Do not wash and wax before placing potatoes in stor-

Sweet Potato Production Guide, Florida Agricultural Extension Service
Circular 97.
Sweet Potato Variety Trials in Florida, Florida Agricultural Experiment
Station Circular S-71.
Electric Hotbeds for Sweet Potatoes, Florida Agricultural Extension
Service Circular 120.
Storage of Sweet Potatoes, USDA Farmers Bulletin 1442.
Utilization of Flue-Heated Tobacco Barns for Sweet Potato Storage,
USDA Farmers Bulletin 1267.
Commercial Growing and Harvesting of Sweet Potatoes, USDA Farm-
ers Bulletin 2020.
Sweet Potato Diseases, USDA Farmers Bulletin 1059.
U. S. Standards for Sweet Potatoes, August 2, 1948.

April 1957

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