There are 650 species available in the world. Nine species were identified in Sri Lanka . Most popular species is Diosvorea 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
Seasonal crop mainly cultivated in home gardens in wet zone and can be cultivated both in wet and dry zone with irrigation.
Climate requirements/ Areas suitable for cultivation
This crop can be cultivated up to 900 m elevation
Optimum temperature is 25-30co. Temperature less than 20 co is not suitable.
Long day (12 ½hrs) needed for vine growth and 10-11 hrs. needed for tuber formation.
Loamy soil with high organic matter 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.
After sprouting Cuttings are taken out from the nursery and plant in the field or direct plant the treated cuttings without using a nursery. 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 about10t/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)
It is important to control weeds, as this crop takes long period for harvest. Before adding the top dress 1 weeding is important.
Vines become yellowing at harvesting maturity. Takes 8-9 month period.
Raja ala – 32 – 35 t/ha
Kakulu ala – 35-38 t/ha
Kukulu ala – 30 – 32 t/ha