Common name: Yam/ Dioscorea
Scientific name: Dioscorea sp.
Family : Dioscoreaceae
Dioscorea or Yam is one of the primitive vegetable crops in the world. In Africa it is cultivated in large scale in tribal area. Tribal peoples of Bangladesh are used Yam in large scale.
Depending on variety it has many shapes. It produced tuber and bulbils which is used as vegetable. Some Dioscorea are highly poisonous.
There are different species if Dioscorea. Among these are edible:
1. Dioscorea alata:
Stem winged and twining antilock direction.
2. Dioscorea opposite:
Stem are wingless also twining anti clock direction. Purple leaf, stem upto 3 m in height . Some are produced in the under ground tuber ,no aerial bulbils.
3. Dioscorea cayenensis:
Having almost character of Doiscorea alata but tubers have short dormance with yellow flesh. Leaves are light green.
4. Dioscorea esculenta:
Stem twining to left with clock wise direction. Leaves simple and entire stem cylindrical normally small tuber produced , bulbils absent.
5. Dioscorea trifida:
Leaves lobed stem square, often winged , several small tubers produced, leaves trifoliate.
6. Dioscorea pentaphylla:
Leaves penta (5) foliate, wild grown, not cultivated,having trifoliate like trifida.
Dioscorea can grow only on tropics. Vegetable crops can grow in the wild condition very little attention.
Climatic Requirements:
Optimum temperature for yam cultivation is 25-32 degree C. It can tolerate up to 45 degree temperature, below 10 degree C plant growth and development are completely stopped. Optimum rainfall is 1000 mm/annum. Long day enhance in vine production and short day enhance in tuber production. That’s why it is grown in tropics and sub-tropics region.
Soil:
Clay loam to sandy loam soil is best for yam cultivation but must be rich in organic matter. Soil having PH 6.5-8.0 is suitable for cultivation.
Propagation:
Dioscorea is mainly propagated by vegetative means i.e. aerial bulbil or underground tuber. Some Dioscorea such as Dioscorea pentaphylla, Dioscorea trifida can be propagated by seed. Generally seed propagation is not practicing, vegetative propagation is normally practising. Aerial bulbil produced Dioscorea alata, Dioscorea opposite and rest dioscorea using mainly by tuber. After harvesting of tuber in the month of Sep.-Oct. tuber kept in sandy soil or in sand. In month of Dec.-Jan. shoot is coming out from tuber or slight sprouting like potato. At least one eye cut should be planted.
Maturing:
Dioscorea generally planted in pit. Pit should be prepared in February- March. During planting time composed applied 20-25 kg/pit. No chemical fertilizer should not be applied during planting in pit. After planting generally in the month of May-June another in Aug.-Sep. To apply:
1) Urea: 300 kg/ha
2) TSP: 100 kg/ha
3) Mop: 320 kg/ha
All fertilizers should be applied in two split doses. 50% applied in May- June and another 50% applied in Aug.-Sept.
Intercultural Operation:
Support is essential for Dioscorea. In our country (Bangladesh) there is no commercial cutivation. For supporting bamboo or forest plantation are usually used for that plant. Weeding and Mulching is essential for Yam cultivation.
Plant Protection:
Disease:
1) Cercospora leaf spot
2) Anthracnose
3) Red rust
Insect:
1) Tuber moth
2) Coleopteran beetle
3) Aphid
4) Mycoplasma
Harvesting:
Tuber becomes harvested 210-300 days after planting. Generally harvesting time is September to October. Cut tuber cannot be kept for propagation. Final harvesting time is November- January. Dioscorea alata can be give 2-3 kg of tuber and other species generally give 1-1.5 kg. Bulbils can be harvested for vegetables.
Yield: 10-12 ton/ ha
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