There are 650 species available in the world. Nine species were identified in Sri Lanka. Most popular species is Dioscorea alata. Dioscorea alata spp is popular with different names like water yam and white yam. Purple color can be seen in any part of the crop.
Other species are
- Dioscorea esculenta
- Dioscorea rotundata
- Dioscorea bulbifera
- Dioscorea pentaphylla
- Dioscorea tomantosa
- Dioscorea trimenii
- Dioscorea oppositifolia
Seasonal crop mainly cultivated in home gardens in wet zone and can be cultivated both in wet and dry zone with irrigation.
Climatic requirements/ Areas suitable for cultivation
This crop can be cultivated up to 900 m elevation
Optimum temperature is 25-30 0C. Temperature less than 20 0C is not suitable.
Long day (12 ½hrs) needed for vine growth and short days (10-11 hours) needed for tuber formation.
Loamy soil with high organic matter content and good drainage is preferred.
Seed/ Cutting requirement
10, 000 seed yam cuttings about 250 g weight is needed for 1ha.
About 250 g weight cuttings are prepared and treated with Fungicide or ash. Plant in a sand bed cowered with straw and supply water after remove the dormancy shoots are coming out from cuttings.
Plough the land. Holes are prepared 1’x1’x1’ feet and fill with organic matter and plant the cuttings.
Treated yam cuttings can be directly plant in the field or plant them in a nursery before field planting. Need to supply sticks about 7 feet for better growth.
For spp with big yams. – 1m x1m.
For species with small yams. – 1mx 0.5 m
Add organic fertilizer about10 t/ha and add inorganic fertilizer according to the DOA recommendation.
Times for apply
TOP dress -1 (1 ½ – MAP)
TOP dress – 2 (3 ½ -4 MAP)
For better growth, need to have good irrigation. Specially in the 1st three months
It is important to control weeds, as this crop takes long period for harvest. Before adding the top dress 1 weeding is important.
Causal Organism: colletotrichum gloeosporiodes
Brown spots can be seen in the leaves and gradually increase the size of the patch. Yellow colour margin can be seen around the brown patch. Finally brown areas become dry and form holes
- Apply carbendazim fungicide
- Select of resistant varieties
- Use of healthy planting material
- Increase sanitation in the field
Causal Organism: Goplana dioscoreae cummins
Yellow – Brown (rust) colour pustules can be seen in the lower side of the leaves
- Cultivation of resistant varieties
- Application of fungicide like Mancozeb / Azoxystrobin
Vines become yellowing at harvesting maturity. Takes 8-9 month period.
- Raja ala – 32 – 35 t/ha
- Kakulu ala – 35-38 t/ha
- kukulala – 30 – 32 t/ha