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Saturday, October 29, 2011

Dioscorea is a seasonal crop

DIOASCOREA

Dioscorea is a genus of over 600 species of flowering plants in the family Dioscoreaceae, native throughout the tropical and warm temperate regions of the world. The vast majority of the species are tropical, with only a few species extending into temperate climates. It is an important staple food crop in the Pacific, Africa and the Caribbean.

Among the tuber crops cultivated in Sri Lanka Dioscorea plays major roll in food security. Dioscorea is a seasonal crop. It means planting in Yala season and the harvest in the Maha season. Special character of this species is remain dormancy period up to planting time.

Easy management, minimum pest and disease attacks, Less input, less attention, can be cultivate in marginal lands as well as high medicinal value gives high demand for Dioscorea spp.
Time of planting
Recommended planting period is the onset of rain in the Yala season. Sand nursery can be used to get germinate those tuber pieces to obtain planting materials on time.
Planting materials
Usage of healthy seed tubers and tubers divided into pieces of 250g are important to maintain successive cultivation. Ash or fungicide must be applied on cutting surface.  
Land Preparation
Loose soils with organic matter more suitable for the Dioscorea spp. Large size pits must be prepared with the rigid soil. Normal size of the pit is about 1X1X1 feets. Straw, coconut husk, paddy husk as well as grass debris can be used as organic matter. Pits is filled with these matter and tubers with active bud can be planted on it.
Dioscorea spp
The most popular Dioscorea spp in Sri Lanka is Dioscorea alata  or Maha vel ala. Apart of that Dioscorea esculenta (Lesser yam) and Dioscorea bulbifera also can be seen. Dioscorea rotandata or the African Dioscorea is the species which is introduced to Sri Lanka.
Recommended spacing
Maha vel ala (greater yam) - 1X1m
Kuda vel ala (lesser yam) - 1X0.5m
Recommended varieties

RAJA ALA
KEKULU ALA
KADIRA
Anthocyanin pigment
Edges of the vine, leaf stalk as well as tuber
Pigments can be seen at the edges of the vine only with germination
No pigments
Shape of tuber
Globular, Occasionally divided tubers
Fan shape tubers
Cylindrical shape small tubers
Weight of tuber
1-2.5kg
3-5kg
100-200g
Flesh colour
Purple colour
White colour
White colour
Taste
Starchy
Medium  starch with mild sweetness
Starchy
Yield
Height yield 32-35t/ha
Height yield 35-38t/ha
30-32t/ha
DOA released varieties
DOA recommended three Dioscorea varieties for cultivation. Those are “Kadira” from Dioscorea esculenta and “raja ala” and “kekulu ala” from Dioscorea alata. Instead of that there are other popular Dioscorea varieties.
Trellising
6 feats and 2.5 inches diameter supporting stalks must be used for each plant. It causes to higher yield. Usage of rope or “V” shape trellising can be use with lack of stalks.
It is very important to train the vine towards trellising.  

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