Ipomoea batatas (L.) Lam.
Syn.: Ipomoea fastigiata Choisy
Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.
- Folk Medicine
- Yields and Economics
- Biotic Factors
Cultivated mainly for the tuber, used as vegetable, eaten boiled, baked fried,
or dried and ground into flour to make biscuits, bread, and other pastries.
Tubers also dehydrated in chips, canned, cooked and frozen, creamed and used as
pie fillings, much like pumpkin. Leafy tops eaten as vegetable and sold in
markets in Malaysia. Greatly esteemed as feed for farm animals; with 3 kg
green sweet potatoes equivalent to 1 kg of corn, with a food value rated
95100% that of corn. Dry vines have feed value which compares favorably with
alfalfa hay as forage (Reed, 1976).
According to Hartwell (19671971), the leaf decoction is used in folk remedies
for tumors of the mouth and throat. Reported to be alterative, aphrodisiac,
astringent, bactericide, demulcent, fungicide, laxative, and tonic, sweetpotato
is a folk remedy for asthma, bugbites, burns, catarrh, ciguatera,
convalescence, diarrhea, dyslactea, fever, nausea, renosis, splenosis, stomach
distress, tumors, and whitlows (Duke and Wain, 1981).
Per 100 g, the root is reported to contain 108121 calories, 68.5 72.3 g H2O,
1.01.7 g protein, 0.20.4 g fat, 25.631.0 g total carbohydrate, 0.71.0 g
fiber, 0.71.0 g ash, 2136 mg Ca, 3856 mg, P, 0.72.0 mg Fe, 1036 mg Na,
210304 mg K, 355,280 mg b-carotene equivalent, 0.090.14 mg thiamine,
0.040.06 mg riboflavin, 0.60.7 mg niacin, and 2137 mg ascorbic acid. The
usual range of values for different constituents is: moisture, 5875; protein,
0.53.5; fat, 0.21.5; N-free extract, 18.037.0; sugars, 2.25.6; fiber,
0.62.5; and ash, 0.61.5%. Indian types with white flesh contain little or no
carotene, while American types with pink flesh contain as high as 5.47.2
mg/100g of caroten. Vitamins present in the tubers are: thiamine, 0.090.14;
riboflavin, 0.050.10; and vitamin C, 1622 mg/100 g. Sucrose and a few
reducing sugars are present, but maltose, mannose, galactose, and pentose
occur, if at all, only in traces. The essential amino acids present in the
total proteins are as follows (calculated to 16.0 g N): arginine, 1.9;
histidine, 1.4; lysine, 4.3; tryptoplian, 1.8; phenylalanine, 4.3; methionine,
1.7; threonine, 3.8; leucine, 4.8; isoleucine, 3.6; and valine, 5.6 g. The
pectic substances (total, 0.78; soluble, 0.43%) present in fresh tubers
contain: uronic acid, 60; and methoxyl, 45%. Other constituents in the
tubers: phytin (1.05%), two mono-amino-phosphatides (probably lecithin and
cephalin), organic acids (oxalic acid, 0.1%), phytosterolin, phytosterol,
resins, tannins, and coloring matter. Sweetpotato contains calcium, 30;
magnesium, 24; potassium, 373; sodium, 13; phosphorus, 49; chlorine, 85;
sulphur, 26; and iron, 0.8 mg/100 g; iodine, 4.5 mg/kg; magnanese, copper, and
zinc are present in traces. The spent pulp, or pomace, left after the
extraction of starch, gave the following values: dry matter, 90.2; protein,
2.5; fat, 0.3; fiber, 9.6; N-free extract, 71.8; mineral matter, 6.0;
digestible protein, 0.4; and total digestible nutrients, 69.0%; and nutritive
ratio, 171.5. Analysis of the dried vines gave: dry matter, 90.7; protein,
12.6; fat, 3.3; fiber, 19.1; NFE, 45.5; mineral matter, 10.2; digestible
protein, 8.9; and total digestible nutrients, 51.7% (C.S.I.R., 19481976). Of
more than a dozen African vegetables, this was the richest in folate (1.931.96
mg/g) (Hug et al, 1983).
Roots may contain the laxative ipomoein.
Tuberous-rooted perennial, usually grown as an annual; top herbaceous, drying
back to ground each year; stems forming a running vine up to 4 m long, usually
prostrate and slender, with milky juice, lateral stem-branches arising from the
short stem and usually not branched; leaves ovate-cordate, borne on long
petioles, palmately veined, angular or lobed, depending on variety, green or
purplish; flowers rare, especially in United States, like common morningglory,
white or pale violet, axillary, funnel-shaped, borne singly or in cymes on
short peduncles; pods round; seeds 14 per pod, flattened, hard-coated,
angular. Fl. summer; fr. late summer and fall (Reed, 1976).
Reported from the Indonesia-Indochina and Middle and South American Centers of
Diversity, sweetpotato, or cvs thereof, is reported to tolerate bacteria,
disease, drought, fungus, hydrogen flouride, high pH, laterite, low pH,
mycobacteria, nematodes, peat, savanna, virus, and weeds (Duke, 1978). Of the
more than forty cvs that have been grown in the US, about 10 are of commercial
value now. These fall into two categories: food types and feed types. They
are further divided into dry or firm types and moist or soft types. The
present outstanding soft-fleshed cvs are 'Porto Rico', 'Nancy Hall', 'Triumph',
and 'Australian Canner'; firm-fleshed types are 'Big-stem Jersey', 'Yellow
Jersey', 'Maryland Golden', and 'Orlis' (Jersey orange). The best,
high-yielding white-fleshed, high-starch feed cv is 'Pelican Processor', which
is somewhat resistant to stem rot, and is especially adapted to the lower
South. Also 'Whitestar' is a white-fleshed cv, high-yielding, high-starch
variety, better adapted to the middle and northerly sweetpotato areas than
'Pelican Processor'. Both contain less carotene than the yellow food types
Native to the American Tropics. Introduced and cultivated in many tropical and
subtropical countries, there becoming important food crop, especially in India,
China, Philippine Islands, and the South Seas Islands (Reed, 1976).
Ranging from Cool Temperate Steppe to Wet through Tropical Thorn to Wet Forest
Life Zones, sweetpotato is reported to tolerate annual precipitation of 3.1 to
42.9 dm (mean of 153 cases = 15.0), annual temperature of 8.4 to 28.5°C
(mean of 152 cases = 23.5), and pH of 4.3 to 8.7 (mean of 88 cases = 6.4).
Well-adapted to tropical and subtropical climates, sweetpotato will grow
successfully over a wide range of climatic conditions where the average
frost-free growing season is at least 5 months. Freedom of frost is not
enough. Days and nights must be fairly warm. Will grow north to Maryland, New
Jersey, New York, Iowa, and Kansas, where it is grown as an annual. Most of
the crop is grown in areas receiving 10 dm or more rainfall annually, but will
grow in areas receiving less than 8.5 dm if irrigated. Rainfall should be well
distributed over the growing season (0.25 cm or more per week) until 2 or 3
weeks before harvest and then about half that. Sweetpotatoes are fairly
drought-tolerant and can survive some rather long dry spells during the summer
after growth is well along. They resume growth with adequate rains, but should
not be considered a dry-weather crop. Low water supply impairs crop quality.
Soils rated good for sweetpotatoes include moderately deep, very friable fine
sandy loams, sandy loams, or loamy fine sands. Soils must be well-drained.
Subsoils of clay are satisfactory unless they are tight and sticky. Some
friable, well-drained loams and silt loams are highly productive. Excellent
soils have surface layers more than 30 cm in depth, those from 1530 cm are
considered good. Slopes should be gentle, with little tendency to become
eroded. If soils are too deep, tubers grow too deep for harvesting machines.
In tropical areas, sweetpotatoes flower and cross-pollinate easily. Hwever, as
plants do not come true from seed, seeds are rarely used for propagation
purposes. In more northern areas where plants never flower, all propagation is
by vegetative means, from transplants produced by bedding mother roots, or from
rooted cuttings. Sweetpotatoes are grown over a wide range on farms of various
types: truck farms, dairy farms, cotton farms, tobacco farms, corn-and-hog
farms, and others. Crops that should be grown on any one field during the
years between Sweetpotato plantings on that field will depend on what other
crops are most profitably grown on that farm. Sweetpotato can follow
successfully any one of a wide variety of crops or be grown on new land.
Sweetpotatoes should be transplanted only after the soil has warmed up well, in
late spring. It is undesirable to grow sweet potatoes on soils too rich in
manures. Plants obtained from bedded mother roots and cuttings taken from
early vine growth are planted about 10 days after frost-free date. Early
transplanting is best. Soil fertility and freedom from diseases must be
maintained. Usually both form new roots so readily that it is unnecessary to
treat them with hormones. Best cuttings consist of ca 20 cm of the ends of
sturdy vines. They may be taken from open-field plant beds or from early
transplants that have produced vines. Most sweetpotato plants are obtained
from slips or plants of seed stock grown in various ways in seedbeds. Plants
are spaced about 30 cm apart in rows about 1.1 m apart (ca 31,250 plants/ha),
or in rows 1.3 m apart (ca 26,350 plants/ha), or in rows 1.6 m apart (ca 21,250
plants/ha). Sweetpotatoes are transplanted by hand or machine. On large
fields, machine planting is more economical and gives more uniform stands.
Three men with a 1-row planter can set 3,500 to 4,000 plants per hour, with one
man driving and 2 setting. With a 2-row planter, 5 men can set 7,000 to 8,000
plants per hour. If the soil is moist enough for setting without water, more
can be set per hour. High yields of high quality sweetpotatoes can be obtained
only on soils of high fertility, good drainage, and suitable texture. Plants
respond well to good soil management and fertilizer practices. The most
profitable yields have been generally obtained with 1.52.25 MT of fertilizer
mixtures containing 24% nitrogen, 8% phosphoric acid, and 810% potash. On
fields where good amounts of green manures or animal manures have been turned
under, often no more than 2% of nitrogen is needed. On lighter sandier soils,
10% of potash is recommended. Fertilizer generally should be applied in two
stages, one just before the ridges are prepared ca 2 weeks before planting,
when 0.75 MT/ha is thoroughly mixed in the soil where the ridge is to be, with
the ridge thrown up so that most of tile fertilizer lies deep in the ridge, and
the remainder applied as top-dressing to the sides of the ridge 2 or 3 weeks
after transplanting. Sweetpotatoes do best on soils that are slightly to
moderately acid. On very acid soils that are deficient in calcium,
applications of ground limestone have markedly increased in yields. It is
undesirable to apply so much lime that the soil is neutralized. Sometimes
sweetpotatoes are grown in the West with irrigation. The time and amount of
water applied vary according to the soil and climate. In general, on
furrow-irrigated lands, six to eight irrigations are applied between
transplanting and harvesting. In all cultivations, weed control must be
pratically perfect before the vines become long enough to interfere with
cultivation. Sweetpotatoes are poor competitors with weeds. Weeds reduce
yields and interfere with harvesting.
Sweetpotato tubers have delicate skins that are very easily broken. The flesh
also is easily bruised, broken, or cut. Wounds are followed by decay unless
they are promptly healed before infection occurs. Roots should not be allowed
to become chilled either before or after being harvested. Sweetpotatoes
develop a substantial amount of the total yield in the last 45 weeks before
frost. Since large yields are necessary, the storage crop is usually allowed
to grow as late as possible without storage quality being damaged by frost.
For large yields 130 to 150 days growth is required. A crop for immediate
marketing can be harvested at any time that the roots are large enough for sale
and that a large enough crop has developed to be profitable. Early harvested
crops are lower in carotene content and in total solids. Probably the best
time to harvest for storage is after the leaves show slight yellowing. The
earliest planted fields should be harvested first. Large plows with 14-inch or
larger shares do less damage to the sweet potatoes than smaller ones. They
should be set deep enough to get under the tubers and not cut them. A 16- to
18-inch tractor-drawn turning plow with a vine-cutting colter in front of it is
probably the best tool for harvesting. Harvesting machines have been developed
that dig the sweetpotatoes, carry them onto a conveyor where dirt is shaken off
and returned to the ground, the roots moving onto a platform where they may be
sorted. Such a machine can harvest 600800 22.5 kg crates a day. The crates
are taken to packing and storage houses for immediate washing, regrading and
repacking, or for curing, storage and later repacking. Harvesting for seed
stock is done at final harvest time. Precautions must be taken to select seed
stock from production hills, from stock free from diseases, and from stock true
to variety. Because the crop has the disadvantage of storing poorly, sometimes
it is sliced and dried in the sun, or packed in sand or straw. With the
development of early and late races, planting for a succession of crop seems
best to shorten periods for storage. A processing plant in the production area
can prepare products for human food (canned and dehydrated), for stock feed,
and for industrial uses, of much material that would otherwise be wasted (Reed,
Average yields vary from 17.5 to 27.5 MT/ha, depending on the cv and growing
conditions (Reed, 1976). In 1979, Texas about 4,400 ha worth more than $5
million. In that year, the US produced 80,000 ha out of a world total of 16
million ha (Patterson, 1979). In 1979, the world low production yield was 400
in Mauritania, the international production yield was 8,355, and the world high
production yield was 80,000 kg/ha in Israel. Other yield figures include 15
MT/ha in Argentina, 1540 in Japan, 40 MT in New England, 20 MT in Sri Lanka,
and 22 MT in Taiwan. Sweetpotatoes have long been considered the second most
important vegetable crop in the US, second only to white or Irish potatoes.
Spain is major producer in Europe; India grows sweetpotato in all states and it
ranks third in importance among tuber crops, exceeded only by potato and
cassava. In China, where it was introduced in 1594, sweetpotato is often used
more than rice and has been used to relieve famines. Per capita consumption in
China is about 28 kg/year; in Japan, 60 kg/year; and in US, 8.5 kg/year.
Production in the United States is about 1 million tons per year.
In India, tops can add up to 1032 MT/ha to 77 MT in 3 or 4 cuttings per year.
The sweet potato is regarded as a valuable raw material for producing alcohol
(also tactic acid, acetone, butanol, vinegar, and yeast). A hectare of sweet
potato can feed more people than a hectare of cereal grains, with less energy
input. "The green weight yield per acre of sweetpotato vines is greater than
the yield of green corn for silage" ca 1550 tons per hectare (Patterson,
1979). Indonesia is planning 2000 gasohol plants, with the fuel coming from
sweetpotato, cassava, and sugar cane (AVRDC Centerpoint, winter 1981/1982).
Sweetpotato is subject to injury from a number of diseases that may attack the
young plants in the hot bed or the growing crop in the field or may cause decay
in storage. The worst of these are stem-rot, black-rot, foot-rot, soft-rot or
ring-rot,and in the Southwest, root-rot. These are described and illustrated,
and control measures are given in Farmers' Bulletin No. 1059, Sweet Potato
Diseases. The sweetpotato is not seriously injured by many insects but the
sweetpotato root weevil has been very injurious in sections of the South,
especially in the Gulf States. This insect threatens to become a serious
menace to sweetpotato growing. Cutworms frequently destroy the young plants by
cutting them off soon after they are set in the field (Williams, 1970).
Agriculture Handbook No. 165 (1960) lists the following as affecting this
species: Albugo ipomoeae-panduratae (white rust), Alternaria sp.
(secondary leaf spot), Aspergillus spp. (secondary storage rot),
Botrytis cinerea (gray-mold rot), Cercospora sp. (leaf
spot), Choanephora cucurbitarum (leaf mold), Coleosporium ipomoeae
(rust), Diaporthe batatas (dry rot of roots, stem rot), Elsinoe
batatas (spot anthracnose), Endoconidiophora fimbriata (black rot of
roots and stems), Epicoccum sp. (storage rot), Erwinia carotovora
(bacterial soft rot), Fuligo violacea, Fusarium oxysporum (surface rot
of roots in storage), F. oxysporum.f. batatas (stem rot),
Helicobasidium purpureum (root rot), Hypomyces ipomoeae, Macrophomina
phaseoli (charcoal rot of stored roots, stem rot), Meliola clavulata
and M. malacotricha (black mildew), Monilochaetes infuscans,
Mucor racemosus (storage rot), Penicillium sp. (bluemold rot),
Pestalotia batatae (on roots), Phyllosticta batatas (leaf
blight), Phymatotrichum omnivorum (root rot), Physarum cinereum, P.
plumbeum, Phytophthora sp. (root rot), Plenodomus destruens (foot
rot of stems and roots), Pyrenophora terrestris (pink rot), Pythium
spp. (rootlet rot, mottle necrosis of mature roots, leak and ring rot in
transit and storage), Rhizoctonia solani (sprout rot, rootlet rot, stem
canker), Rhizopus spp. (soft rot, ring rot of stored roots),
Schizophyllum commune (dry rot of roots), Sclerotinia sp.
(storage rot following chilling), S. minor (sprout rot in seedbeds),
Sclerotium rolfsii (southern blight, cottony rot), Septoria
bataticola (leaf spot), Streptomyces ipomoea (soil rot),
Trichoderma spp. (punky rot of stored roots), Verticillum
albo-altrum (wilt) (Ag. Handbook 165, 1960). Several viruses are known to
infect sweetpotatoes: A virus, B virus, Feathery mottle (sweetpotato internal
cork virus), Mottle and Mosaic, Tobacco mosaic, Vein-clearing, and Mizugusare
disease. Internal brown spot is due to boron deficiency. Because
sweetpotatoes are a tuber crop, many nematodes have been reported on the crop,
including the following species: Aphelenchoides besseyii, Aphelenchus
avenae, Belonolaimus gracilis, B. longicaudatus, Criconemella onoensis,
Ditylenchus destructor, D. dipsaci, Helicotylenchus multicinctus, H. cavenessi,
H. concavus, H. microcephalus, H. pseudorobustus, Hemicriconemoides
cocophillus, Meloidogyne hapla, M. incognita, M. incognita acrita, M. javanica,
Nothotylenchus affinis, Pratylenchus brachyurus, P. coffeae, P. pratensis, P.
penetrans, P. scribneri, P. thornei, P. zeae, Quinisulicius capitatus,
Radopholus similis, Rotylenchulus reniformis, Scutellonema brachyurum, S.
clathricaudatum, Tylenchorhynchus annulatus. T. claytoni, and Xiphinema
americanum. Insects attacking sweetpotato plants include the following
species: Long-horn beetles (Cerambicid), Sweetpotato flea beetle
(Chaetosnema confinis), Wireworms (Conoderus amplicollis, C. falli,
C. vespertinus), Sweetpotato weevil (Cylas formicarius elegantulus),
Cucumber beetles (Diabrotica balteata and D. undecim-punctata),
American plum borer (Euzophera semifuneralis), Wireworm (Melanotus
communis), Tortoise beetles (Metriona sp.), Flower beelte
(Notoxus calcaratus), Variegated-cutworm beetles (Systena blanda, S.
elongata, S. frontalis), Sweetpotato leaf-beetle (Typophorus nigritus
viridicyaneus). Methods for control should be obtained from local
agricultural agents (Reed, 1976).
Complete list of references for Duke, Handbook of Energy Crops
- Agriculture Handbook 165. 1960. Index of plant diseases in the United States.
- Duke, J.A. 1978. The quest for tolerant germplasm. p. 161. In: ASA Special
Symposium 32, Crop tolerance to suboptimal land conditions. Am. Soc. Agron.
- Duke, J.A. and Wain, K.K. 1981. Medicinal plants of the world. Computer index
with more than 85,000 entries. 3 vols.
- Hartwell, J.L. 19671971. Plants used against cancer. A survey. Lloydia 3034.
- Hug, R.S., Abalaka, J.A., and Stafford, W.L. 1983. Folate content of various
Nigerian foods. J. Sci. Food & Agr. 34(4):404406.
- Patterson, D.R. 1979. True rootssweet potatoes. Texas Ag. Progress/Winter,
- Reed, C.F. 1976. Information summaries on 1000 economic plants. Typescripts
submitted to the USDA.
- Williams, L. 1970. Sweet potato (Ipomoea batatas L.). Typescript.
Last update Wednesday, January 7, 1998 by aw