Sweet Potato

Botanical Name Ipomoea batatas L.

Chromosome No. 2n = 90
Family Convolvulaceae
Common Name Sakarkand/ Mitha Alu
Uses
 Tubers are canned, dehydrated and floured and are important sources of starch, glucose, pectin,
Sugar syrup and industrial alcohol.
 It is the cheapest source of calories and its calories production per unit time and per unit area
is highest in sweet potato among tuber and root crops.
 Its leaves and vines are mainly utilized in feeding live stock.
 Tender tops and leaves used as vegetable in Africa, Indonesia and Philippines.
 ‘Weikang’ a product from leaves is effective in raising immune function and controlling
hypercholesterolemic symptoms.
 Sweet potato is cultivated for its sweet root tubers. Since roots contain 16% starch and 4% sugar,
it is used for production of industrial starch, syrup and alcohol. Rich in carbohydrate, starch and
quality depends on sugar content which vary from 3 to 6%.
 Mostly sucrose and few reducing sugars are present such as Maltose, Mannose, galactose and
pentose occur in traces.
 During storage and cooking sugar percentage increases.
 Some cultivars have 5.4 to 20 mg/100g carotene. Yellow and orange fleshed cultivars are mostly
rich in carotene.
Origin and Distribution
 Sweet potato is a native of tropical America specifically South America or central America or
North west of south America.
 In India major Producing States are Orissa, Bihar, Uttar Pradesh and Madhya Pradesh but not
Jammu & Kashmir.
Table 1 : Average Composition of Potato Tuber
Moisture 70% Fat 0.2%
Carbohydrate 27% Fiber 1.0%
 Protien 1.5 - 2.0 %
Mineral and Vitamines Present in Potato (mg/100g)
Calcium 46 Iron 0.8
Phosphorus 49 Magnesium 24
Pottasium 373 Sulphur 26
Sodium 13 Thiamine 0.08
Chlorine 85 Riboflavin 0.04
Niacin 0.70 Carotene 0.18
Vitamine C 24
.
Area and Production
China is the bigest producer with 70% world area and 84.4% of world production. The highest
productivity was noted in Isreal (34.9 t/ha) followed by Egypt ( 30.0t/ha) and Japan ( 25.6 t/ha).
India occupies 12 th position in area (0.131 mha) with production of 1.5 mt with a productivity of 11.4
t/ha.
With respect to productivity highest is AP followed by TN, UP, Karnataka, WB ,Odisha and
Chattishgarh.
About 80% of the total sweet potato growing area is occupied by Orissa, WB, AP and UP.
In Orissa it is mainly cultivated in Bolangir, Koraput, Baragarh, Ganjam, Dhenkanal, Koenjhar and
Sundergadh districts.
Growth and development
 Grows best at temperature of > 24°C with low night temperatures and growth is restricted by
cold weather and plant damaged by temp below 10°C. It needs a minimum frost free growing
period of 4-6 months.
 High temperature and high soil moisture leads to excessive growth during starch
accumulation period at the cost of root development.
 20 to 30°C is better for tuber formation.
 Long days (16 hr.) stimulate vine length and short days (9 hr) promote tuberisation.
Flowering
 It is a short day plant. Long nights and high temperature favour flowering.
 11.5 hrs day is ideal for flowering. It is a self incompatible plant.
Soil
 Sweet potato requires well drained fertile soil rich in humus. Best soil is sandy loam with clay
subsoil and it can also be grown on loamy to clay loam soils.
 Heavy clay soils which become hard after drying are not suited.
 Highly sandy soils cause development of long, cylindrical and thin tubers.
 In compact soils, tuber yield is low due to poor aeration.
  It is an mildly acid tolerant crop and requires a pH of 5.8 to 6.7.
 If pH is below 5.2, liming is necessary. Acidic and saline soils reduce growth of stem and roots.
 Neutral and high pH may cause pox and scarf diseases.
 Sweet potatoes are relatively sensitive to saline and alkaline soil conditions.
 Crop cannot withstand water logging and good drainage is essential.
Climate
 Moderately warm climate is ideal (21 to 26.7°C)
 Temperature less than 20°C effects tuber formation.
 For tuber formation 25 to 30°C is ideal. Even slight frost kills the foliage.
 It requires plenty of sun shine and moderate rain fall.
 A well distributed annual rainfall between 75 and 150 cm is favourable.
 High rain fall and long photo period (16 hr) promote vine growth and reduces tuber yield. Tuber
yield, number of tubers and total biological yield were promoted by 9 hr light.
 It can be grown from 40°N to 32°S and on equator up to an altitude of 2200 MSL.
 Sweet potato is a moderate drought tolerant crop and gives good yield without irrigation in
semi-arid regions.
 However, yield is more when rain is received during early part of growing season.
Sweet Potato Cultivars
 There are many varieties, which are differentiated mainly by the shape, size, colour of tuber,
flower colour and leaves. However, there are two important groups of varieties from the market
point of view, based on outer colour (rind) of tuber. They are usually grouped either as white
or red type.
 White type is supposed to be less sweet and more fibrous whereas red types are shorter in
duration and has a better quality flesh. Sweet potato varieties differ in shape, size and colour of
leaves, tubers and nature of tuber flesh.
 A number of local cultivars like Badrakali chuvala, Chakkaravalli, Anakomban and Kottaram
chuvala are grown in Kerala.
 The Central Tuber Crops Research Institute (CTCRI), Thiruvananthapuram developed
quite a good number of varieties and name of few varieties are given below:
Varsha ,Sree Nandini , Sree Vardhini , Sree Ratna , Sree Bhadra ,Sree Arun ,Sree Varun, Pusa
Safed Pusa Sunehri, . Pusa Lal (IARI) Pusa Harit , Kissan, Pusa Bharati, Kalmegh, Gouri,
Shankar etc..
Propagation
 It is often propagated vegetatively and rarely through seeds.
 Propagated mainly by vine cuttings and also by tubers.
 Freshly harvested matured vines should be used.
 Vines of one crop are used as planting material for the next crop.
  For seed propagation scarification is required due to hard seed coat. Plant from seeds are
poorly grown with low tuber yield.

Tubers
 Medium sized healthy tubers free from disease, pests and bruises are planted in nursery
(Primary) at 5 to 10 cm depth with 60x25 cm spacing.
 Sprouts are cut after 40-45 days and planted in secondary nursery.
 Cuttings of 20-30 cm length planted at 60x 25 cm in main field.
 Sufficiently grown vines are used to make cuttings for main field preparation.
 A mature tuber produces 5-7 sprouts and 100kg tubers produces 7000 shoots.
 For one hectare 250 kg tubers, 100 m2 primary nursery, and 500 m2 secondary nursery area
are needed.
 Micro propagation technique is also being followed.
Raising Nursery
Primary Nursery
 Cuttings for planting are multiplied in two nurseries - primary and secondary.
 Tubers in primary nursery are planted three months ahead of planting.
 A nursery area of 100 m2 is required to raise vines for planting one hectare.
 Ridges are prepared at 60 cm apart and tubers of 125-150 g weight are planted at 25 cm spacing.
 1.5 kg urea is applied at 15 days after planting and irrigate as and when required.
 Clip off vines to a length of 20-30 cm at 40-45 days after sowing tubers for planting in
secondary nursery.

Secondary Nursery
 A 500 m2 secondary nursery is required to plant cuttings obtained from 100 m2.
 Plant the cuttings at 25 cm apart in ridges taken at a spacing of 60 cm.
 5 kg urea may be applied at 15 and 30 days after planting in nursery.
  Clip off cuttings in 20-30 cm length after 45 days from middle and top portion of vines with 3-
5 nodes are optimum for tuber production.
 Cut vines are stored with intact leaves in shade for two days prior to planting in main field.
Preparation of Main Field and Planting
 Vines are planted during June-July for a rainfed crop.
 Under irrigated conditions, plant during October-November in upland and during January-
February in low lands for summer crop.
 Main field is prepared by making ridges of 25-30 cm height at 60 cm apart after thorough
ploughing.
 20-30 cm long vines are buried horizontally with 2-3 nodes below soil, leaving the remaining
portion above soil. Vines are also planted in an inclined position with half of its length buried
in the soil.
Planting Methods
 Mound method, Ridge and furrow method, Bed method and Flat method
Land Preparation Land is ploughed to a depth of 20 cm and harrowed to pulverise the soil
Interculture
 Weeding and earthing up of the soil has to be given between 15-30 days after planting along
with top dressing.
 Vines are to be lifted at nodes to prevent rooting and to facilitate better rooting and tuber
development at the basal end.

Manures and Fertilizers

 Apply 5 tonnes of farmyard manure/ha at the time of preparation of 50% of N, full P and K to
be applied as basal dose.
 Remaining 50% of N is applied one month after along with weeding and earthing up.
Excess Nitrogen application leads to excessive vegetative growth at the cost of tuber development.
Biofertilizers like Azatobacter and Azospirillum can be applied to reduce the Nitrogen fertilizer doses.
Azospirillum 2kg/ha vine dipping + 10 kg/ha soil application reduced application of nitrogen up to
2/3rd of RD. Earthing up at 15 or 30 days after planting can increase yield, RDF is NPK: 75:50:75
kg/ha. In AP SP- Maize - Vegetables (Common crop rotation in practices)
Growth Substance
CCC at 250 to 1000 ppm increased yield. GA inhibited tuberization and Kinetin enhanced tuberization
Irrigation During rabi and hot seasons, 12-14 irrigations supplying 112-150 cm are required at an
interval of 10 days for heavy yield. Critical stage of irrigation during tuber development i.e 50-60
days after planting.
USDA Package
Season: June-July (Rainfed crop), September -October(Irrigated crop) or October-December (Irrigated
crop) with 3-4 node cuttings: 50,000/ha and FYM 10t/ha NPK: 75:50:75 kg/ha 50% as basal and 50%N
after 5-6 weeks of planting
Spacing and Season of Planting Spacing 60x30 cm.
Season North India February-March and September –October
Tamil Nadu September : Kerala September – December and May . It is grown both in kharif and rabi
season but in WB main growing season is rabi.
Harvesting Depends on variety and its maturity period 120 to 180 days .Harvested when leaves turn
yellow and begin to shed. Maturity can be ascertained by cutting tubers and latex from mature tuber
dries up without turning black. Irrigate 4-6 days prior to harvesting when soil is compact. Before
harvesting, vines are cut and tubers are dug up by using spade or fork. Avoid mechanical injuries while
digging. Bulking rate is a reliable parameter for fixing the maturity period and it vary with cultivar i.e. H-
633 (75th days), H-268 (120 days), etc. Harvesting is done by digging out tuber with pick-axe when
leaves turn yellow in colour. Tubers are cleaned and packed in gunny bags for marketing.
Yield : 6-9 t/ ha for rainfed crop & 12-15 t/ ha under average management. Indian average: 6 to 7 t/ha.
USDA Package: 25 to 30 t/ha , In addition 2.5 -10 t/ha tops are produced as good cattle feed.

Storage
 Before storage curing is must.
 Curing is done at 29-32°C, 85-90% RH, for 4 to 7 days heap tubers, curing heals wounds.
 Store at: 10-12°C at 85-90%RH for months together.
 At 15- 12°C & RH of > 70% it can be stored for 4 to 12 weeks.
 Red skinned varieties store better than white skinned varieties. Tubers are stored better at
15°C and 85% RH. Tubers can also be stored for 2-3 months in a pit covered with straw.
Post-Harvest Management
 After harvest, tubers are spread in partial shade for 5-6 days, for healing and curing.
 They should be stored in semi-dark condition in a well ventilated room.
 This type of storage invites infestation of pest and diseases.
 In some parts of the country, tubers are stored in a layer of dry sand/soil after curing under
ambient conditions.
 For storing, graded tubers free from sweet potato weevil and bruises should be selected.
 Farmers store the graded tubers by keeping in a pit shade and covering the pit with paddy
straw.
 Finally, the heap is plastered with mud or cow dung slurry.
Sweet potato products Sweet potato products

SQUASH & BATATA SHAKE Sweet potato curd Sweet potato lacto-pickle

ALCOHOL MEDICATED CURD

WINE
Preserved sweet potato

Pest and Diseases

Sweet potato weevil (Cylas formicarius): is the most important pest causing severe damage to the crop.
Adult weevil makes puncturing on vines and tubers. Grubs bore and feed by making tunnels. Even
slightly damaged tubers are unsuitable for consumption due to bitterness. Yield loss is up to 100% in
severe cases. On an average, 20-55% tuber loss occurs.