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Crop Recommendations
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Sweet Potato
The cultivation of sweet potato has traditionally been confined to varying growing systems such as open land highland, rice fallow system, under shade, owita and homestead conditions. Sweet potato has remarkable ability to convert solar and soil energies into carbohydrates giving impressive yields under marginal and stress situations having low input requirements and little attention, wide adaptability, flexibility in crop management and non-seasonality make sweet potato a viable crop in all agroecological zones excluding high elevations. Recommended Varieties
Semi-vine plant type with entire to very slightly lobbed leaves. Root tubers have dark pinkish skin with highly variable tuber shapes which are fusiform.
Semi-vine plant type with entire leaves. The mature leaves are green in colour and the tender leaves are light green with purple at margin. Petioles are light green with purple at leaf end and petiole base. Root tubers are fusiform shape with purple coloured skin.
It is a polycross hybrid and maternal parent is a native variety Beli-batala. It has a bushy plant type with deeply cut leaf laminas. Vines and leaves are green in colour with purplish green tender leaves. Root tubers are highly uniform and fusiform in shape having pinkish orange skin.
Wariyapola white is a mutant, originated from the variety Wariyapola red. Semi-vine plant type with entire to very slightly lobbed leaves. Root tubers are highly uniform and fusiform in shape having white skin.
Semi-vine plant type, the leaves are entire to slightly lobbed, vines are yellowish green except tender vine apices are slightly pigmented. The root tubers are round elliptical shape with pink skin.
It is a natural selection from Kalutara district. BW - 8 is a semi-vine type plant with light green stems. Leaf type is moderately lobbed with purple colouration at the base of the leaf on the lower side. Tuber shape is egg shaped with tapering ends and skin colour is white.
It is a polycrose hybrid and material parent is recommended variety CARI-426. Semi-vine plant type with numerous major branches. Entire vines are green in colour except the very tender vine apices which are slightly pigmented with moderately lobbed leaves. The root tubers are round to elliptical shape, highly uniformed with white skin.
Field Establishment Sweet potato is grown in the tropical, sub tropical and warm temperate regions of the world. Sweet potato is a sun loving crop. It requires considerable amount of rain during the growth period and a dry period during root formation. Warm sunnydays and cool nights are very much favourable for storage root formation in sweet potato. Tuber yields are reduced considerably if drought occurs within first six weeks after planting.
Sweet potato can be successfully grown in a variety of soils, however well drained sandy loam soils are best suited. On heavy clay soils shoots grow well, but yield of tubers will be poor with deformed tubers.
Till to a depth of 25cm. Soils must be well drained and well aerated for a successful tuber growth. Ridge and furrow method, mound method, narrow bed and broad bed method are practiced in sweet potato cultivation in different areas. Ridge and furrow method and narrow bed method are better than other methods.
Vine cuttings are suitable for planting. The vine tip cuttings are found to be best to get higher tuber yield from sweet potato. In some varieties recurrent use of vines as planting material for more than 5,6 seasons showed marked decrease in yield. For these varieties root tubers can be sprouted and get cuttings. About 55,000 - 60,000 cuttings are required to plant one hectare.
Under rainfed conditions, plant with the Yala and Maha rains. In the wet zone in both Yala and Maha and in the dry zone in Maha season only.
Under irrigated conditions, planting can be done at any time of the year.
No of cuttings and method of planting depend on the method of bed preparation. Spacing between 2 plants is 20cm. In ridge and furrow method cuttings are planted at a spacing of 90cm x 20cm. Vines of 20-25cm length with at least 5 leaves are found to be ideal as planting material.
Crop Management Application of fertilizer should be done before 45 days to get a maximum vegetative growth of the crop. After 45 days vegetative growth should be minimise and root production must be increased. Basal fertilizer should apply after 15 days and top dressing at 45 days after planting.
For fertile soils, fertilization should be discouraged because sweet potato when over fertilized grows vines and leaves at the expense of fleshy roots.
Weeding and earthing-up Sweet potato is a quick growing crop and it covers the soil quickly and suppresses most of the weeds. However, weeding may become necessary particularly in the early stages of growth. To protect the crop from weeds at least 2 weedings and earthing up has to be given with in 45 days after planting along with fertilizer application.
Insect control Sweet Potato Weevil: Cylas formicarius
* Adults feed on epidermis of vines & leaves scraping oval patches and make round feeding punctures on external surface of tubers. * Lavae feed inside the vines caused malformation, thickening & cracking of affected vines. * Lavae tunnel tubers, deposit frass & it causes decay minutes before planting. 2. To avoid cracking soil at the base of the vine, earthining up of soil and regular watering is necessar Diseases are not serious in sweet potato. However root rot caused by Fusarium has been identified in sweet potato. The symptoms are yellowing of leaves and later drying of vines and rotting of roots.
Control measures are improve drainage, ensure field sanitation and use resistant varieties. Harvesting & Post-harvest Technology
Harvesting The crop attains maturity in 3 1/2 to 4 months after planting depending upon the variety and environmental conditions. The maturity of tubers can be determined by cutting fresh tubers. The cut surface of the immature tubers gives a dark greenish colour while in mature tubers, the cut ends dry clearly. After removing the vines tubers are dug out without causing injury.
Post-harvest handling The harvested roots can be transported to the market or can be stored. The tubers are normally cured by keeping in a open place for 4 to 7 days. After curing sweet potato roots can be stored for 3 months.
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