HORDI Crop – Yams

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Yams

Dioscore spp

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

  1. Dioscrea esculenta
  2. Dioscrea rotundata
  3. Dioscrea bulbifera
  4. Dioscrea pentaphyla
  5. Dioscrea tomantosa
  6. Dioscrea trimenii
  7. Dioscrea oppositifolia

Seasonal crop mainly cultivated in home gardens in wet zone and can be cultivated both in wet and dry zone with irrigation.

Released Varieties

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.

Soil

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.

Nursery Management

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.

Land preparation

Plough the land. Holes are prepared 1’x1’x1’ feet and fill with organic matter and plant the cuttings.

Planting

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.

Spacing

For spp with big yams. – 1m x1m.

For species with small yams. –  1mx 0.5 m

Fertilizer

Add organic fertilizer about10 t/ha and add inorganic fertilizer according to the DOA recommendation.

Times for apply

Urea  kg/ha

TSP kg/ha

MOP kg/ha

Basal fertilizer

65

150

60

TOP  dress -1  (1 ½ – MAP)

65

60

TOP dress – 2  (3 ½ -4 MAP)

65

60

Water supply

For better growth, need to have good irrigation. Specially in the 1st three months

Weed Control

It is important to control weeds, as this crop takes long period for harvest. Before adding the top dress 1 weeding is important.

Pest Management

Disease Management

Causal Organism: colletotrichum gloeosporiodes

Symptoms:

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

Management:

  • Apply carbendazim fungicide
  • Select of resistant varieties
  • Use of healthy planting material
  • Increase sanitation in the field

Causal Organism: Goplana dioscoreae cummins

Symptoms:

Yellow – Brown (rust) colour pustules can be seen in the lower side of the leaves

Management:

  • Cultivation of resistant varieties
  • Weeding
  • Application of fungicide like Mancozeb / Azoxystrobin

Harvesting

Vines become yellowing at harvesting maturity. Takes 8-9 month period.

Yield

  • Raja ala – 32 – 35 t/ha
  • Kakulu ala – 35-38 t/ha
  • kukulala – 30 – 32 t/ha