SWEET POTATO CULTIVATION
Sweet potato / Ipomea batatus is cultivated for its sweet root tubers. It is mainly used for culinary purposes after boiling, steaming, baking or frying and also as animal feed. The local names for sweet potato are Shakarkand, Chilakada Dumpa, Sarkaraivalli Kizhanku, Genasu, Ratala, Kandamula, Mathura Kizhangu, Shakkaria, Shakkar, Rang aloo and so on.
The roots contain 16% starch and 4% sugar and therefore it is used for the production of industrial starch, syrup, and alcohol. In India, it is grown mainly in AP, Telangana, WB, Assam, MP, Maharashtra, Bihar, TN and Orissa. Sweet potato requires well-drained fertile soil rich in humus. It is a perennial herb with trailing vines with a cluster of medium-sized tubers. For cultivation purpose, it is treated as an annual with duration of 90 to 120 days.
Sweet potato has an extensive fibrous root system both at stem cuttings and at nodes touching the soil. Some roots act as storage organs for storing reserve food. Storage roots may be fusiform, spindle or globular in shape and surface is smooth. Its skin has white, red or light copper color. The flesh may be white or with different combinations of orange and red. Leaves are simple, alternate and stipulate. They vary in size and shape, occasionally in the same plant. Leaf shape is an important character for identifying clones. All clones do not flower and in flowering ones, duration and initiation of flowering vary.
Flowers are bisexual. Fruit is a capsule with false septa. The seed coat is hard and impervious to water. Hence, scarification is required for promoting germination. Sweet potato is sweet as the name suggests and therefore can be simply boiled, peeled and eaten. It is filling and serves as a good snack item or even at lunch-time. Some dishes made from sweet potato are candied sweet potatoes, sweet potato medallions, Shakarkand ki chaat, Sweet potato fries, Sweet potato tikkis, sweet potato puffs and so on.
Shakarkand is an important source of starch, glucose, sugar syrup and industrial alcohol. It is the cheapest source of calories. It produces highest food calories among the tuber and root crops. It is ideal for people looking to gain weight. The different varieties of sweet potato are Varsha, Sree Nandini, Sree Vardini, Sree Ratna, Sree Bhadra, Sree Arun, Pusa Safed, Cross-4, Kalmegh, Rajendra Shakarkand-5, Konkan Ashwini, Pusa Sunheri and so on.
It is essential to wash the sweet potato well after buying and then use it. It has a good shelf life and can be stored at room temperature like normal potatoes. It is rich in beta-carotene and antioxidants.
Image source – agrifarming.in
Sweet potato varieties
Image source – sunagri.in
Image source – fruitsvege.com
Process of growing Sweet Potatoes
⦁ Time / Season / Climatic conditions –
Sweet potato requires a warm humid tropical or sub-tropical climate with temperatures around 21 – 26 °C. It requires frost-free regions to cultivate well. It also requires a well-distributed rainfall between 75 – 150 cm for optimum production. Heavy rainfall destroys the crop. The crop needs adequate sunshine at least 5 months a year. It can tolerate drought conditions but not water stagnation. The crop can grow easily at altitudes of 2200 m above sea level.
Rainfed crop – June – July, Sept-Oct
Irrigated crop – Oct – Nov – uplands, Jan – Feb – lowlands
⦁ Seed rate / Spacing –
Sweet potato can be propagated by tubers clips or vine cuttings. Propagation by vine cutting is a very common practice. About 40 – 50 thousand cuttings are required for planting a hectare of land. The cutting is grown in the nursery from the old vines or from clips produced on the tubers planted in the nursery beds. The vine cuttings are planted either on ridges for monsoon crop or in flat-bed in low rainfall area. Terminal cuttings from full-grown plants are reported t give better growth and yield than the basal or model cuttings. Each cutting should have at least 4 nodes.
The vine cuttings are planted at about 60 cm from row to 30 cm within the row. Keeping the end bud free roots are formed in the central part of vines which is put inside the soil. It is better to plant the cuttings after them 8 – 10 minutes in D.D.T 50 % solution.
⦁ Soil type / Land preparation / Irrigation –
Since the tuber growth takes place inside the soil, it needs loose, friable soil for better root development. It can grow in well-drained, sandy loam and clay sub-soil. Heavy clay soil, which becomes hard after drying checks the development of the tubers and highly sandy soils cause the development of cylindrical pencil like a tuber. High fertile soils favor luxuriant vegetative growth. Soil should be well drained for successful cultivation. Sweet potato can be grown with a pH range of 5.6 – 6.6.
Plough the field to a fine tilth. The soil depth should be at least 30 cm. Form ridges and furrows at 60 cm apart. Sweet potato can also be grown in beds. 30 – 50 cart-loads of FYM should be given at the time of soil preparing. 50 – 60 kg N, 50 – 60 kg P and 100 – 120 kg K/ha should be applied. Half N, full P and K should be applied at the time of planting. Remaining half N should be applied 30 days after planting.
In Kharif season, the crop needs less irrigation the most critical stage of moisture supply is 40 days after planting. Excessive moisture supply deteriorates the quality of tubers. During Rabi and dry seasons, 10 – 12 irrigations are given @ 8 – 10 days interval. The soil requires sufficient moisture 40 – 45 days after planting. The frequency of irrigation depends on soil moisture holding capacity and climatic conditions.
⦁ Weed Management / Pest Control –
Intercultural operations and crop rotation help reduce and control weeds. Conduct 2 weeding and earthing operations 2 and 5 weeks after planting. Prevent development of small, slender tubers at the nodes by turning the vines occasionally during the active growth phase. Sweet potato can be rotated with rice. As a mixed crop, it can be grown with colocasia, amorphophallus, etc.
Sweet potato can be controlled by destroying the crop residues of the previous crop and using weevil-free planting materials. You can also apply Eupatorium odoratum leaves as mulch @ 3 tons/ha at 30 DAP. Apart from these integrated pest management practices, you can reridge the crop 2 months after planting and installing pheromone traps @ 1 trap / 100 m² area to collect and kill the male weevils.
Soft rot can be controlled by spot drenching with Carbendazim 1 g/lit.
⦁ Harvesting –
Time of harvesting depends on the variety. Before harvest, vines are cut and tubers are dug with the help of a fork. Sweet potato is harvested when leaves turn yellow and shed. Judge the maturity by cutting tuber. If latex dried up without turning black, it is sure that the sweet potato is matured. Irrigate the crop 4 – 6 days prior to harvest to facilitate harvesting. Take care that tubers are not injured while harvesting.
Harvesting is done by digging out the tuber with pick-ax when leaves turn yellow in color. Tubers are cleaned and packed in gunny bags for marketing. The average yield is 6 – 9 tons/ha for rain-fed crop & 12 – 15 tons/ha under average management.
Under rain-fed conditions, the yield is 80 – 100 quintal/ha while under good management and irrigated conditions, the yield is about 250 quintal / ha. In addition to tubers 10 – 25 tons of vines are produced per hectare.
⦁ Benefits of Sweet Potato –
⦁ Sweet potato is an excellent source of fiber, vitamin B6, E and C
⦁ It is good for the heart
⦁ It helps in controlling blood sugar due to low glycemic index
⦁ It helps in relieving stress
⦁ It is good for digestion and contains a good amount of starch
⦁ Sweet potatoes have strong immunity and anti-inflammatory properties
⦁ It helps in preventing cancer
Nutritional value of sweet potato – as per Wikipedia
% Daily Value*
Total Fat 0.1 g 0%
Saturated fat 0 g 0%
Polyunsaturated fat 0 g
Monounsaturated fat 0 g
Cholesterol 0 mg 0%
Sodium 55 mg 2%
Potassium 337 mg 9%
Total Carbohydrate 20 g 6%
Dietary fiber 3 g 12%
Sugar 4.2 g
Protein 1.6 g 3%
Vitamin A 283% Vitamin C 4%
Calcium 3% Iron 3%
Vitamin D 0% Vitamin B-6 10%
Vitamin B-12 0% Magnesium 6%