Important Points

• The most probable ancestor of sweet potato is – Ipomoea trifida.
• Sweet potato is a perennial crop.
• Commercially propagated by vine cuttings (4000 cutting/hac).
• Sweet potato has a low respiratory rate.
• It is less tolerant to salts but tolerant to soil acidity.
• It is a deep-rooted crop.
• Male sterility is present in sweet potato.
• Excessive rainfall and long day conditions encourage vine growth and reduce tuber yield.
• Anthesis -4:00-5:00 AM
• Sweet potato is a short-day plant.
• The ridge and furrow method is best for raising crops.
• The roots are mainly used for human food after boiling or steaming or frying and as animal feed.
• It is used to make industrial starch, syrup and alcohol.
• In India, it is mainly grown in Andhra Pradesh, Assam, Bihar, Tamil Nadu and Orissa.
• China is the largest producer.
• India is the largest producer of sweet potato in southeast Asia and the fourth largest producer globally.

Nutritional value (per 100 g edible portion)

Moisture 70.2 g, Energy 120 kcal, Protein 1.65 g, Vitamin A 14,187 IU, Fat 0.4 g, Vitamin C 2.4 mg, Carbohydrates 28.2 g, Iron 0.8 mg, Fiber 3 g, Calcium 22 mg, Starch 16%, Sugar 4%

Climatic

Sweet potatoes can be grown in tropical and subtropical climates. It requires a warm and humid climate. The optimum temperature is 21-27°C, and below 20°C critical temperature for tuberization. Sweet potatoes are one of the most drought-resistant vegetable crops.

Soil

Sweet potatoes require well-drained fertile soil rich in humus. Sandy loam soil with clay is ideal for tuber production. Heavy soils result in smaller tuber sizes. The ideal soil pH should be between 5.8 and 6.7.

Varieties

Other Varieties – Punjab Sweet Potato-21, Sree Kanaka, H-41, H-42, Co 3, Co CIP 1, Kanjanghad, Kiran, Samrat, Bhuban, Gold Rush

Sowing time

• Rainfed area: June-July
• Irrigated area: October-November

Seed rate

Use 25,000-30,000 vines cutting in per acre or 50,000-60,000 vine cuttings/ ha. Sowing 35-40kg tubers in half a kanal land is done to raise vines from February to March.

Seed treatment

Place the tubers in a plastic bag and then soak them in concentrated sulfuric acid for 10-40 minutes.

Nursery Raising

Sweet potato is mainly propagated by vine cuttings of 25-30 cm in length. For planting, the cuttings are propagated in two nurseries- primary and secondary. In primary nurseries, tubers are planted three months before planting. A nursery area of ​​10m2 is required for growing vines for a one-hectare plantation. Ridges are prepared at a distance of 60 cm and tubers weighing 125-150 g are planted and irrigated as required. For planting in the secondary nursery, cut the vines at a length of 20-30 cm after 40-45 days of sowing of tubers. The secondary nursery requires 500 m2 of space for planting cuttings. Plant the cuttings at a distance of 25 cm in ridges 60 cm apart. 5.0 kg urea may be applied after 15-30 days of planting in the nursery. After 45 days, cut cuttings of 20-30 cm in length from the middle and top part of the vines. The cut vines along with the leaves are stored in the shade for two days before planting them in the main field.

Field Preparation

2-3 ploughings up to 15 cm depth are sufficient to make the soil friable. After ploughing thoroughly, the main field is prepared by making 25-30 cm high ridges at a distance of 60 cm.

Spacing

60 cm x 30 cm

Manures and Fertilizers

Add 5 tonnes of farmyard manure per hectare while preparing the ridges. The recommended dose of fertilizer is 50:25:50 kg NPK per hectare. Full phosphorus, potassium, and half the nitrogen amount should be given as a basal dose. The remaining half amount of nitrogen is given after one month.

Irrigation

Generally, rainy-season crops do not require irrigation for long periods. During Rabi, 12-14 irrigations are necessary at 8-10 days to ensure better root development and yield.

Intercultural operations

Hoeing, weeding and earthing up are essential at an early stage of growth to control weeds and to improve physical condition of the soil. Incorporation of Fluchloralin at 1.0 kg/ha in the soil as pre-planting control the weeds.

Harvesting

The crop is ready to harvest in 120-180 days after planting. Harvesting is done when the leaves turn yellow in colour and start to shed. The maturity can also be judged by cutting roots and drying tuber latex without turning black, giving a good indication of maturity.

Yield

• Rainfed condition: 8-10 t/ha
• Irrigated condition: 30-40 t/ha

Insect-pests

Sweet potato weevil (Cylas formicarius): It is the most important pest causing severe damage to the crop. Adult weevils bore into vines and tubers. Grubs tunnel and bore into the stems and feed. Tubers are unfit for consumption as they are bitter. Yield losses are up to 100% in severe cases.

Control: Spray Malathion 50 EC @ 1.5-2.0 ml/lit at an interval of 10-15 days.

Diseases

1. Cercospora leaf spot: First reported in Africa. Brown spots appear on leaves which later coalesce and form large lesions. Warm, wet and humid weather favours the spread of this disease.

Control: Spray Indofil M-45 or Zineb @ 2 g/liter of water.

2. Stem rot or wilt (Fusarium oxysporum batatas): Leaves of the affected plant turn yellow, develop round sunken spots and plants wilt.

Control: Dip in 0.2% solution of Agallol or Aretan before planting.

3. Black rot (Ceratocystis formbriata): This disease occurs both in the field and in storage. Infected vines show yellow, diseased and black spots on the underground portion of the stem.

Control: Dip in 0.2% solution of Agallol or Aretan before planting.