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Sweetpotato
Botanical Name – Ipomoea batatas
Family – Convolvulaceae

Importance

• The botanical name of Sweet potato is Ipomoea batatas.
• This crop is mainly grown because of its sweet taste and starchy roots.
• The tubers are rich source of beta-carotene and are used as anti-oxidants.
• It is an herbaceous perennial vine having lobed or heart shaped leaves.
• Its tubers are edible, smooth skin, tapered and long.
• It has wide color range of tuber skin i.e. purple, brown, white and purple which contains wide range of flesh i.e. yellow, orange, white and purple.
• In India about 2 lakh of land is under cultivation of sweet potatoes.
• In Bihar, West Bengal, Uttar Pradesh and Orissa are the major growing states in India.

 
Varieties

1)Punjab Sweet Potato-21: 

• The vines of this variety are medium long in length.
• It has broad shape and dark green color leaves, long and thick stem, 4.5 cm inter nodal length and has 9 cm petiole length.
• It contains deep red color tubers having white flesh which is 20cm long and 4cm wide.
• The variety gets mature within 145 days.
• The average weight of tuber is 75g.
• The tuber contains 35% of dry matter and 81mg/g of starch.
• It gives an average yield of 75 qtl/acre.

Other state varieties:

1) Varsha:

• It is recommended to grown in Maharashtra.
• It is suitable to grown in rainy season.
• It gives an average yield of 62.5 qtl/acre.

2) Konkan Ashwini:

• This variety is developed to be cultivated in Maharashtra.
• It is short duration crop and gives high yield.

3) Sree Arun:

• It is an early maturing variety having pink color skin and cream color flesh.
• The variety is developed by Central Tuber Crop Research Institute (CTCRI), Sreekariyam.
• It gives an average yield of 83-116 qtl/acre.

4)Sree Kanaka:

• The variety is developed by Central Tuber Crop Research Institute (CTCRI), Sreekariyam.
• It has cream color skin tuber which has dark orange color inner flesh.
• It gives an average yield of 41-62.5 qtl/acre.

5)Sree Varun:

• The variety is developed by Central Tuber Crop Research Institute (CTCRI), Sreekariyam.
• It contains cream color skin of the tuber.
• It is an early maturing variety which gets mature within 90-100 days.
• It gives an average yield of 80-110 qtl/acre.

Improved varieties:

H-41, H-42, Co 3, Co CIP 1, Sree Vardhini, Sree Rethna, Sree Bhadra, Sree Nandini, Kanjanghad, Gouri, Sankar and Kiran.

 
Soil and Climate

Soil –

• It is grown in variety of soil types ranging from sandy to loamy soil, but it gives best result when grown under sandy loam soil having high fertility and good drainage system.
• Avoid cultivation of sweet potato in very light sandy and heavy clayey soil as it is not good for tuber development.
• It requires pH ranging from 5.8-6.7 is best for sweet potato cultivation. 

Climate – 

• It requires a moderately warm climate (21-26°C) with soil pH of 5.5-6.5.
• Heavy rainfall, high temperature and excess cloudiness encourage vegetative growth.
• In sweet potato, close spacing is generally recommended to achieve maximum root yield.

 
Season and Planting

Time of sowing:
For optimum yield, tubers should be sown in nursery beds in the month of January to February and the optimum time for planting vines in the field is in the month of April to July.

Method of Propagation

Seed rate:

• Use 25,000-30,000 of vines cutting in per acre land.
• Sowing of 35-40kg tubers in half a kanal land is done for raising vines in February to March month.
• Vines are then planted in the main fields in one acre land.
• Seed treatment:
  Place the tubers in plastic bag and then soak them in concentrated sulphuric acid for 10-40 minutes.

Preparation of Field

• For sweet potato plantation, the land should be well prepared.
• To bring the soil to the fine tilth, before sowing land must be ploughed 3-4 times followed by planking’s.
• The field should be weed-free.

Crop Rotation

• Sweet potato + Rice crop rotation can be taken up successfully under irrigated conditions.
• Sweet potato can be planted in the month of December-January after second harvesting of rice.

Fertilizer doses

Nutrients Value (kg/acre)

Fertilizer Requirement (kg/acre)

•  Apply FYM (Farm Yard Manure) @100 qtl/acre. Along with FYM apply fertilizer dose in terms of CAN @125 kg/acre, SSP @155 kg/acre and MOP @35 kg/acre.
• Full dose of K2O and P2O5 is applied at the time of planting.
• Nitrogen dose is applied in 2 splits i.e. first at the time of planting and secondly should be applied after 5 weeks of planting.

Weed Control

• Apply Metribuzine 70WP@200gm per acre or Alachlor@2Ltr per acre before sprouts emergence.
• On 5-10% sprout emergence and ridge are infested with weeds then only apply Paraquat@500-750ml per acre.

Irrigation

• After planting, irrigation is given once in 2 days for period of 10 days and thereafter irrigation is given once in 7-10 days.
• Irrigation must be stopped before 3 weeks of harvesting.
• But before 2 days of harvesting one irrigation is necessary.

Plant Protection

1) Sweet potato weevils :

Symptoms-

They damage the plant by feeding themselves on the epidermis of vines and leaves.

Treatment:

To control weevils spray of 200 ml Rogor @150 ltr water per acre.

2) Tuber Moth :

Symptoms-

• It is major pest in field as well as in storage.
• It make tunnel in potato and feeds on flesh.

Management-

• Use healthy and diseased free seeds for sowing.
• Use only well decomposed cow dung.
•  If infestation is observed take spray of Carbaryl@400gm/100ltr of water.

3) Aphid : 

Symptoms-

• Adult and nymphs, both suck the sap thus weaken the plant.
• In severe infestation, they cause curling and deformation of young leaves.
• They secrete honey dew like substance and Sooty, black mould is developed on affected parts.

Management-

• Cut the foliage according region timing, to check infestation of Aphid.
• If Infestation of Aphid and Jassid observed take spray of Imidacloprid@50ml or Thiamethoxam@40gm/acre/150Ltr water

4.Tortoise beetles: Aspidiomorpha miliaris 

Diseases

1) Black scurf : Monilochaetes infuscans

Symptoms

• Copper-skinned sweet potatoes usually have brown lesions, and red-skinned sweet potatoes have black lesions.
• Lesions enlarge until the entire surface of the root is discolored.
• Affected tissue can be easily scraped off.
• Most scurf infections result from the use of infected propagating material.
• The fungus can also survive in crop debris in the soil for 1 to 2 years.
• Management-

• For planting use diseased free tubers.
• Before sowing, seed treatment with Mercury is essential..
• If land kept fallow for two years then severity of disease is reduced.
• Grow sweet potatoes after a 3- to 4-year rotation with other crops
• Cut transplants at least 1 inch above the soil line, and dip them in a fungicide..

2) Early blight : 

Symptoms-

• Necrotic spots observed on lower leaves.
• The fungus due which infestation occurred lies in soil.
• It rapidly spread in high moisture and low temperature.

Management-

• Avoid mono-cropping of crop and follow crop rotation.
• If infestation is observed, take spray of Mancozeb@30gm or Copper oxychloride@30gm/10Ltr water at 45 days 2-3 times at 10 days interval.

3) Common scab : 

Symptoms-

• It survives in field as well as in storage.
• Disease is spread rapidly in low moisture condition.
• Light brown to dark brown lesion are appeared on infected tubers.

Management-

• Use only well rotten cow dung for application in field.
• Use diseased free seeds for planting.
• Avoid deep planting of tubers.
• Follow crop rotation and avoid mono cropping in same field.
• Before sowing, treat seeds with Emisan [email protected]% (2.5gm/Ltr of water) for five minutes.

4) Black Rot: Ceratocystis fimbriata

Symptoms:

• Small, circular, slightly sunken, dark brown spots are the initial symptoms of black rot.
• Tissue near the discolored area may have a bitter taste.
• Eventually, the entire root may rot.
• Roots may appear healthy at harvest but rot in storage, during transit, or in the market.

Management

• Control black rot with crop rotation, since most crops are unaffected by the disease.
• Propagate plants from healthy stem cuttings.
• Cure roots immediately after harvest. (Cure roots – 85 to 95 %  F and 85 to 90 % relative humidity for 5 to 10 days.)
• Apply a postharvest fungicide.
• Do not wash and package roots showing symptoms of black rot.
• Fumigate storage structures.

5.Rhizophus soft rot: Rhizopus stolonifer

Symptoms

• Infection and decay commonly occur at one or both ends of the root, although infection occasionally begins elsewhere.
• If the humidity is high, the sweet potatoes become heavily “whiskered” with a grayish black fungal growth.
• This feature distinguishes Rhizopus soft rot from other storage rots.
• The color of the root is not significantly altered, but an odor is produced that attracts fruit flies to the area.

Management

• Carefully handle sweet potatoes during harvest to prevent unnecessary wounding. This is the most important control method for soft rot.
• Properly cure roots immediately after harvest.
• Store roots at 55 to 60 degrees F.
• Apply a recommended fungicide after harvest.
• Do not allow sweet potatoes to be exposed to sunlight for extended periods (to prevent heat damage) or to be chilled in the field.

6.Bacterial soft rot: Erwinia chrysanthemi

Symptoms

• Lesions on storage roots often have a dark brown margin.
• Some storage roots appear healthy from the outside but are decayed internally.
• Mother roots often decay in plant beds.
• In the field, brown to black, water-soaked lesions appear on stems and petioles.
• Eventually, the stem may become watery and collapse, causing the ends of vines to wilt.
• Usually, one or two vines may collapse, but occasionally the entire plant dies.

Management

• Carefully handle sweet potatoes during all stages of production. This is the most important control method for bacterial soft rot.
• Select mother roots from fields free of the disease.
• Cull roots infected during storage.
• Use vines cut above the soil surface for transplanting.
• Use a handling system that does not involve immersion of sweet potatoes in water.

7.Charcoal Rot: Macrophomina phaseolina

Symptoms

• In the field, brown to black, water-soaked lesions appear on stems and petioles.
• Eventually, the stem may become watery and collapse, causing the ends of vines to wilt.
• Usually, one or two vines may collapse, but occasionally the entire plant dies..
• The disease is sometimes confused with black rot and Java black rot.

Management

• Properly cure sweet potatoes immediately after harvest to reduce the incidence of charcoal rot.

Yield

20-25 t/ha of tubers in 110 – 120 days.