COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
AGRICULTURAL EXTENSION SERVICE, UNIVERSITY OF FLORIDA
FLORIDA STATE COLLEGE FOR WOMEN
AND UNITED STATES DEPARTMENT OF AGRICULTURE
A. P. SPENCER, Director
SWEET POTATOES A WAR FOOD
AND FEED CROP
By J. LEE SMITH
The sweet potato is an important crop on many Florida farms,
not so much because of the acreage utilized in producing it but
because of the number of uses to which it is put. With sweet
potatoes a comparatively large amount of food and feed can be
produced on a small acreage. A survey made of 1 crop a few
years ago showed that an average of 135 bushels per farm was
AGRICULTURAL EXTENSION SERVICE
produced by those reporting. Approximately 29 percent was
used as food by the people on the farm, 38 percent was sold for
cash or traded for other produce, and 22 percent was fed to
livestock, mostly hogs and cows. The remaining 11 percent was
lost through decay.
A light, well drained sandy loam soil with a clay subsoil is
ideal for sweet potato production, although the crop can be
grown successfully on a wide range of soils. The soil should
hold moisture well but must be ridged where the water table is
high, keeping the potatoes well out of the water. It should be
moderately fertile-on very fertile soils the crop tends to run
to vines at the expense of potatoes. A moderate quantity of
well rotted organic matter in the soil is desirable. Less cultiva-
tion is required on comparatively "new" land. Potatoes should
not be grown on the same land more often than once in 3 years.
There are available to Florida growers many varieties, includ-
ing the Porto Rico, Nancy Hall, Big Stem Jersey, Dooley and
Triumph. Porto Rico is by far the most popular. Its flesh is
orange yellow to salmon in color, very sweet, and moist and soft
in texture. Big Stem Jersey is the most popular variety having
a dry, mealy texture. The Louisiana Copper Skinned strain of
Porto Rico is recommended as the best producing and best quality
potato for Florida farms, Coker's Improved as next best.
THE PLANT BED
Types.-The type of bed is determined by the number of plants
wanted and the speed with which it is desired to grow them.
The fire-heated bed will produce plants in the shortest time after
bedding. This may be flue-heated or pipe-heated. A manure-
heated bed or a coldframe will produce plants more quickly than
will open beds. The fire-heated bed is used almost altogether
by growers of commercial potatoes or plants. A good "pulling"
of plants can be secured from any type of bed by the time the
danger of frost is past by bedding those earliest to which the
least heat is applied. If plants must be "pulled" before the dan-
ger of frost is over they may be "heeled in" and kept watered
where they can be protected from cold until they can be set or
they may be "sheared back," letting the tops grow out again to
produce strong stubby plants.
Disinfecting Seed.-To produce disease-free potatoes one must
begin with disease-free seed, use disease-free soil and manure in
the bed, and plant in a field on which no potatoes have grown for
several years and over which no water from a potato field has
flown. The seed need to be disinfected also to kill off blackrot
and other disease spores.
Seed can be disinfected by soaking potatoes for 10 minutes in
a borax solution made by stirring 1 pound of borax in 5 gallons
of water or for 8 minutes in a solution of corrosive sublimate
containing 1 ounce to 8 gallons of water. This can be done also
by pouring a solution made from mixing 1 pound of Semesan
Bel and 71/2 gallons of water over the potatoes just before bed-
ding. These materials are poisonous and any potatoes so treated
should not be used for food or feed.
If an old frame is used all trash should be cleared up and
burned and the frame disinfected.
For details, see U. S. Department of Agriculture Circular No.
AWI-27, Farmer's Bulletin 1059, or Farmer's Bulletin 999.
Seed Potatoes.-By selecting seed from high producing hills of
commercial size potatoes in the fall and bedding these, one can
prevent his potatoes from "running out" and probably improve
them. When bedding a nick can be cut in each potato to deter-
mine if the quality has been maintained. Where this is not done
one needs to secure a new lot of seed from someone who follows
this practice or from a breeder every few years. For seed it is
best to use a commercial size potato free from cuts, bruises and
disease spots. Potatoes grown from vines are freer of disease
than those grown from slips.
From 7 to 10 bushels of potatoes are required to produce
enough plants at the first pulling to set an acre. If 2 or 3 pull-
ings are made only 3 or 4 bushels are required.
Bedding.-A southern exposure is desired for the bed. The
north and west sides of the frame should be higher than the
south side. The bed can be located on the south side of a build-
ing or in some other sheltered spot. Bedding should be done on
a warm day or after the soil has been warmed up from artificial
heat. Except when growing plants in the open, glass cloth, glass
or muslin (without holes) soaked in linseed oil should cover the
bed to keep out cold winds and rain and hold in the heat. In an
excavation 5 or 6 inches deep or inside the frame of the bed,
about 4 inches of sand or loamy soil reasonably free of weed seeds
is put and leveled. On this the potatoes, not touching each
other, are placed by hand, after which they are covered about 1
inch with sand or loamy soil. The bed should then be watered
thoroughly by sprinkling. When the plants begin to show
through the surface, an inch or more of sand or soil should be
added, to develop long shanks and a good root system. A layer
of fine straw, grass or sawdust may be used for this purpose and
prevent the soil from packing.
Managing.-If glass or cloth covering is used the bed must be
sprinkled with water from time to time as needed. The temper-
ature beneath the cover should run from 700 to 80 and during
bright days it must be controlled by ventilation. As the date for
transplanting approaches and when weather will permit, the
plants must be hardened to outdoor conditions by leaving the
covering off most or all of the time for about 10 days before
transplanting to the field. The plants must be protected from
frost, however, and it may be necessary to cover the bed at night.
PLANTING SEED POTATOES
Sweet potatoes can be grown by planting seed pieces cut from
the tip and stem ends of string or small potatoes. These cut
pieces should be not more than 2 inches long and from 1/ to 1
inch in diameter at the large end. Large pieces are apt to grow
into large mature potatoes, which is undesirable. These should
not be split or scarred and should be disinfected (as potatoes
for bedding) and planted at once. They may be covered 3 to 4
inches deep, spaced, fertilized and cultivated the same as plants.
This practice, however, is not generally recommended.
Heavy applications of nitrogen tend to make the potatoes go
to vine. A commercial fertilizer analyzing from 3 to 4 percent
nitrogen, 8 percent phosphoric acid and from 5 to 8 percent pot-
ash will be very satisfactory for sweet potatoes. From 500 to
800 pounds per acre should give excellent yields when applied
to early planted potatoes to be harvested in the fall. From 1,200
to 1,600 pounds should be applied when they are to be harvested
within 4 months, if a fair crop is to be expected. The fertilizer
should be applied in the drill and thoroughly mixed with the soil
a week or more before the plants are set. Smaller quantities of
fertilizer can be used when the potatoes are for farm and home
As much as 10 or 12 tons of manure per acre free of any sweet
potato vines or refuse can be used if applied broadcast in late
winter or early spring. "Trodding" the land with cattle in cen-
tral Florida until a thin coating of manure is on the land is a
good practice. Phosphate and potash will need to be applied
also if no complete fertilizer is used.
PREPARATION OF LAND
The land should be plowed and fitted for sweet potatoes prac-
tically the same as for corn. It should be well pulverized to a
depth of 6 or 7 inches.
The ridge method of planting is satisfactory in Florida. The
ridge is usually thrown up with a turnplow a week or 10 days
before setting, so that the soil may become thoroughly settled
and compact and the fertilizer may become thoroughly mixed
with the soil. The top of the ridge may be leveled off with a
hoe or a drag just ahead of setting, thus destroying any young
weeds that may have started to grow. The higher the water
table or the poorer the drainage the higher the ridge should be
to keep the water below the potatoes.
SETTING THE PLANTS
The number of plants required per acre depends upon the fer-
tility of the soil and the amount of fertilizer used. On fair potato
land when the amount of fertilizer recommended in this circular
is used, 12 to 13 thousand plants are required per acre. This
will put them in 31/2-foot rows and spaced approximately 12
inches in the drill. If soil is poorer or less fertilizer is used,
fewer plants are used and one can expect smaller yields.
In planting small acreages the plants are dropped about the
proper distance apart on the ridge and an implement known as
a shovel or dibble made of a piece of board or lath sharpened
to a concave flat point or end is used in planting them. The
planter places the notch over the tip end of the root or over the
middle of the cutting and forces it into the soil, leaving the top
of the plant and both ends of a cutting above ground. If the
soil is very moist the opening is filled by a stroke with the
"shovel" or the planter's heel; if not, the hole is filled by pouring
about a half pint of water in it, watering the plant.
With large acreages transplanting machines will facilitate
planting. These machines usually open a furrow, water the
plants and close the soil about them as boys sitting on the ma-
chine place the plants in the furrows. Under favorable condi-
tions a machine should plant 3 or 4 acres per day.
Clean cultivation is necessary until the vines cover the ground.
The loose earth, usually a balk left in the middles during ridg-
ing, should be worked toward and up the sides of the ridge. A
turnplow is often used for this. A cultivator with disks can be
used for throwing soil toward the rows and cultivating the sides
of the ridge. Small sweeps or scrapes or a 1-horse stock are also
used. Shallow cultivation should be practiced regularly and hoe-
ing may be required to keep down weeds. It may be necessary
to turn the vines from one side of the row and then to the other
to permit the last cultivation or 2, but the crop should be laid
by as soon as land is covered with vines.
SWEET POTATO WEEVIL
The sweet potato weevil resembles an ant, having a brick-red
thorax or waist, distended body and dark-blue prominent head
and beak. It burrows into or through the potato, leaving excre-
tions which make the potato unfit for food and, if many infest
it, unfit even for feed. It enters the vines and tubers at the
crown more often than not. All farms west of the Suwannee
River are free from the weevil but many in other parts of the
state are infested.
Sweet potato weevils can be eradicated from any farm, since
they can live and multiply only on sweet potatoes and morning
glory vines. Old banks, beds and fields of potatoes are to be
thoroughly cleaned and old potatoes and strings destroyed by
feeding or burning. No potatoes must be allowed to grow, either
volunteer or set, within a quarter of a mile of an infested area
for a year or more. Any farmer securing potatoes or plants
should be certain that they come from a weevil-free farm. (For
details, see Farmer's Bulletin No. 1020.)
Early market sweet potatoes may be harvested when they
reach marketable size, regardless of season or maturity, because
they are dug, crated and sent to market for immediate consump-
tion. The main crop, intended for storage and used on the farm
or shipped to distant markets, should be well matured before
digging. Maturity is indicated by yellowing of the vines. The
potatoes certainly should be dug before the first killing frost.
Implements used for cutting the vines and digging the pota-
BIL.L OF MATERIALS
1 pc. 2"x2" angle iron 27" long. 3 under-serrated, mower :nife
1 3/4"x6" coil spring (old auto 2 pcs. "x2"x" strap iron
brakerod spring) for clamp.
1 l1"x" flathead bolt. 2 2"x3/8" flathead bolts.
3/4"x6" coil spring hole
".i "-."li \ iAngle iron\ / -0 -
A sweet potato vine cutter which is easily made and works well. (Courtesy
South Carolina Extension Service.)
toes should be the best ones available, run at a depth and in a
manner that will do the least damage to the potatoes.
In digging small plots a hoe for cutting the vines and a spading
fork are the most desirable implements to use, but for larger
crops a turnplow with colter or some other fine cutter fastened
to the beam, or a regular sweet potato plow, is more practical.
Potatoes should be picked up and handled with care, laid on the
bed for drying and then into a hamper for carrying to the place
of storage. Throwing them into rough baskets, boxes, tubs or
wagon boxes against one another or tramping on them causes
many breaks in the skin through which disease-producing spores
enter and cause decay. When green or immature potatoes are
harvested in the summer they must be removed quickly, as the
hot sun will blister them and start decay.
As potatoes are picked up for removal from the field the mar-
ketable ones should be separated from the small, cut, cracked,
unmarketable ones and stored separately. When stored this way
any class of potatoes can be removed without disturbing the
others. Decay will be less.
When large quantities of potatoes are produced and stored a
specially built storage house is desirable. If an old storage house
is used all old potato scraps should be removed and storage house
or bins disinfected. Flue-cured tobacco barns can be successfully
used for storing sweet potatoes. (See Farmers' Bulletin No.
1267, Utilization of Flue-Heated Tobacco Barns.) Any building
used for storage of potatoes must be so constructed that uniform
temperature can be maintained, influence of outside temperature
reduced to a minimum during cold, hot and rainy seasons, and
plenty of floor and roof ventilation is provided (See Farmers'
Bulletin No. 1442, Storage of Sweet Potatoes.)
If the late crop is to be banked, as most Florida sweet pota-
toes are, pine or other clean straw material should be placed on
level or slightly elevated ground (so water will not stand) and
the potatoes piled on it.
These piles should be left open until the potatoes are cured or
there is danger from cold. If the potatoes seem to be in danger
of blistering by the hot sun they can be covered with straw or
grass similar to that used under them. Before a freeze arrives
the sides should be walled with dirt piled over the straw. A hole
should be left in the top of the bank to permit further ventilation
and a shelter put over the top to prevent rain from entering.
If the potatoes had to be walled up before they cured or before
the excess water was dried out, the walls can be removed for a
while after the danger of freezing is over until such curing is
secured. If ventilation is desired after walling a vent can be
provided on 2 sides by placing through the walls inverted troughs
without ends. These can be closed with dirt in case of a freeze.
GRADING AND MARKETING
When shipped, sweet potatoes should be placed on the market
according to U. S. grades. When placed on the local market they
should be at least free of strings, decay, dirt, trash and cracked
or very large potatoes. An attractive pack of good medium-
sized sweet potatoes will almost always demand attractive prices.