Dioscorea spp                   


 


   

    Dioscorea spp

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.

Fertilizer Recommendation

Fertilizer application must be done before 4.5months to obtain optimum growth rate. Not necessary to apply fertilizer after that.

Time of application	Amount (kg/ha)
	TSP	Urea	MOP
Basal Dressing	65	150	60
1 Top dressing (1.5-2 months after planting)	65	-	60
2 Top dressing (3.5-4 months after planting)	65	-	60

Weed Management

Weed control must be done prior to top dressings. Mulching is important to weed control as well as soil and water conservation.

Pest and Disease Control

Pests and diseases are not common in Dioscorea spp. Diseases can be controlled by using trellising. Fungal diseases can be controlled by using cupper containing fungicide.

Harvesting
Dioscorea vine growth interrupt and yellowing will show the harvesting time clearly. From that point onward harvesting can be done up to vine died. Thus harvesting can be done according to marketing demand.