Botanical Name: Ipomea batatus.
Sweet potato is a important tuber crop grown for starchy food in tropical and sub tropical countries. India it is called as ‘Sakharkanda’.
COMPOSITION AND USES
Sweet potato contains starch. Mainly sweet potato is used after boiling, baking and frying. It is 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. Sweet potato is also used to feed livestock.
Sweet potato requires warm weather of at least four to five months. It needs temperature range between 21 to 27 0 C. a well distributed rainfall of 75 to 150 cm is desirable. It is a tropical and subtropical crop. It can not tolerate heavy rainfall which induces excessive vegetative tuber development. Is does not stand frost.
Since the tuber growth takes place inside the soil, it needs loose friable soil for better root development. It can grow in 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 development of cylindrical pencil like tuber. In compact soil tuber yield is low due to poor aeration. Such soils also creates harvesting problem. High fertile soils favor luxuriant vegetative growth. Soil should be well drained for successful cultivation. 5.8 to 6.7 soils Ph is suitable.
Times of planting vile cutting and growing season have marked effect on the yield of sweet potato. In Maharashtra it is planted in September – October. For Kharif crop planting in May- June the cutting from sprouts and higher yield of tubers cutting of 24- 30 cm long are planted. Vines are buried inside the soil in the middle and one node at each and kept exposed.
METHODS OF PLANTING
Sweet potato can be propagated by tubers clips or vine cuttings. Propagation by vine cutting is a very common practice. The cutting are 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 four nodes. The vine cuttings are planted at about 60 cm from row to 30cm within the row. Keeping the end bud free roots is formed in the central part of vines which is put inside the soil. It is better to plant the cuttings after them 8 to 10 minutes in D.D.T 50 % solution.
About 40- 50 thousand cuttings are required for planting an hectare of land.
In Maharashtra white fleshed with red skin colour sweet potatoes are grow. The cultivars are from clonally selection. Variation among the cultivar exists in respect of skin and flesh colour, shape and size of tubers. Mostly local varieties are grown. There are varieties like H- 268, Pusa Safed, Pusa red, Pusa sunahari, NO- 4004, S- 30, Klamath and recent one Skarkand – 5. The period of maturity ranges between 90- 140 days. In general it is ready for harvesting in 120 days.
- Varsha: It is released for Maharashtra suitable for rainy season. It is the high yielding ( 150 q/ ha). it belongs to the group varieties of sweet potato.
- Konkan Ashwini: A sweet potato variety Konkan Ashwini is released for cultivation in Maharashtra. It is a short duration, dual seasonal and high yielding variety.
Manures and Fertilizer:
30- 50 cart load 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 ½ N, full P and K should be applied at the time of planting. Remaining ½ N should be applied 30 days after planting.
In Kharif season crop needs less irrigation the most critical stage of moisture supply is 40 days after planting. Excessive moisture supply deteriorates the quality of tubers.
Intercultivation to suppress weed growth is necessary to obtain high yields. Earthing up is followed. Earthing up after 13- 30 days of planting increases the yield. In early of the crop weeding is essential as in later stage vine growth suppresses the weeds.
Time of harvesting depends on the variety. Before harvest vines are cut and tubers are dug with the help of 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.
Under rain fed conditions yield upto 80- 100 quintal / ha obtained while under good management and irrigated condition yield upto 250 q/ ha is obtained. In an addition to tubers 10 – 25 tonnes of vines are produced per hectare.
- Sweet Potato Weevil:
Sweet potato weevil is a most serious pest of this crop. A red and blue ant like weevil that makes holes in the stem and tubers. The pale yellow grub of this pest having no feed bores into the vines.
- Cultural practices such as destruction of alternate host, removal of infested vines and tubers, deep ploughing of land harvest and earthling up to prevent entry of weevil into tubers have been found effective for controlling for this pest.
- This pest can be controlled by spraying the crop with Endosulfan (Thiodane 35 EC) @ 2 ml per liter of water of carbaryl @ 2.5 gm per liter of water.
- Sweet Potato Sphinx: It is a serious leaf eating caterpillar of sweet potato. A stout long horn caterpillar that completely that defoliate the plants.
- Hand picking and destroying the caterpillar is the best method, if infestation is less.
- This pest can be controlled by spraying the crop with lead arsenate of Endosulphan, if infestation is very severe.
DISEASE OF SWEET POTATO
- Leaf Spot: Large brown spots appear on leaves.
This disease can be controlled by spying with Zineb (Dithane Z- 78) or Mancozeb (Dithane M – 45) @ gm pre liter of water at an interval of 15 days.
- Black Rot:
It is primarily a storage rot of tubers but may also occur in the filed, in the filed. Infested foliage become yellow and sticky in appearance and black canker are seen on the portion underground and grey black circular spots occur on fleshy roots.
- Careful sorting of tubers before storage and rotation of crops are helpful in reducing the incidence of the disease.
- The seed tubers should be treated with mercuric chloride solution (1 in 1000) or 2.5 per cent borax solution.
- Soft Rot:
Storage rot of tubers and their tissue become soft and stringy.
- Avoiding brushing and injuring the tubers at harvesting is the best method of controlling this disease.
- The walls and floors of storage room should be disinfected before the storing tubers.