Organic Cultivation of Yam

 

 

 

Yam, Dioscorea spp, is grown for their edible tubers. It was believed to have originated in parts of Africa (West Africa) and Asia.

In West Africa, Nigeria produces the greatest quantity of yam. The crop is commonly cultivated in parts of the Eastern Nigeria and other areas such as Agbon, Benin, Asaba, Oyo, Zaria, Kwara, Plateau, Niger, Kaduna, Benue and Cross River State.

In Ghana, large quantities of yam is grown in Northern part of Ashanti.

 

 

Varieties

White yam (Dioscorea rotundata)

Water yam or purple yam (Dioscorea alata)

Yellow yam (Dioscorea cayenensis)

Air-potato yam/Aerial yam (Dioscorea bulbifera)

Asiatic or Lesser yam (Dioscorea esculenta)

Bitter yam (Dioscorea dumetorum)

Chinese Yam (Dioscorea opposita)

Potato yam (Dioscorea babatas)

Chinese yam (Dioscorea polystachya)

Indian yam or Cush-cush yam (Dioscorea trifida)

Japanese mountain yam (Dioscorea japonica)

 

 

Method of Propagation

Yams are propagated by:

(1)    Tubers (seed yam) which are either planted whole or cut into smaller pieces called setts.

(2)    Seeds but this is mainly done for breeding purposes.

(3)    Vine cutting and tissue culture.

 

Climate and Soil Requirement

The temperature of 20 – 30^oC is ideal and an annual rainfall of 1100 – 2200mm equally distributed throughout 8 – 10 months is ideal. Ideal soil pH is between 5.5 and 6.5.

Yam is planted when day length is more than 12 hours.

A high level of soil moisture is necessary for excellent tuberization. Yam requires a loose, free drainage and fertile sandy soil.

The shape of the tuber is influenced by the depth and softness of the soil.

 

Land Preparation

The land is cleared of existing vegetation. The herbaceous parts are ploughed into the soil while the rest is discarded.

The seed bed used may be holes dug in the ground, mounts, heaps or ridges depending on the soil type.  

 

Planting

In riverine areas, planting is done in October to December to enable the yams mature before the area gets waterlogged in July or August the following year.

In the hinter land, planting is between March and June, if the crops are to be rain-fed.

For seed rate: 3 – 4 tons per ha are used. For ware yam production (large yams sold in the market for consumption), seed yams or sett weighing 1kg are used while for seed yam production, setts weighing about 0.4kg are used.

Spacing: Spacing depends on the nature of the soil as well as the purpose for which the crop is grown

For sole cropping, 1m x 1m spacing is ideal whereas, if the yam is intercropped with other crops like maize, a spacing of 1.5m x 1.5m is recommended.

Closer spacing generally produces higher yields per ha but smaller tubers are produced.

Planting is done at an angle of 45^OC in a slanting position.

Planting depth: 15cm especially for those planted very early before the rainy season.

Mulching: Continuous mulching of the entire ridge top is better than capping (using of the mulching material to cover the area in which the yam sett is placed). This helps to keep the soil cool around the planted sett.

 

Staking

This is done to hold the yam vines to ensure a good yield.

Staking materials include branch or stem of plants,  bamboo, palm frond as well as some strong grass stem.

Yam vines should be staked with stakes of about 2m long. If the yams are big enough, they’d be supported with long sticks of about 5m.

This helps the stake to stand upright and also spread the yam leaves enough for them to receive sunlight energy.

The vines are tied up the stakes in an anti-clockwise direction except for few species e.g D. bulbifera and D. domentorum which climb in a clockwise direction.

Early planted yams begin to germinate 20 – 60 days after planting. If after 60 days, the planted yams did not germinate, a replacement may be necessary.

 

Organic Fertilizer Application

Compost or farmyard manure is used, it is better added at the time of planting. About 20 – 25 metric tons of manure per hectare of land is adequate.

Yam is a heavy feeder and therefore require a lot of nutrient for optimal yield. This is why farmers always grow yam first in a newly open land i. e land that have  been laid fallow for more than 4 years.

The organic fertilizers are used to supplement less fertile soils, 60g per plant about 2-3 months after planting.

 Where the soil pH is less than 5, liming is done during tilling to reduce the soil acidity.

Also, vermicompost, produced by chemical disintegration of organic matter by earthworms, is an ideal blend of plant nutrients with worm enzyme and probiotics to boost the crop performance. It contains higher amount of nutrients, hormones and enzymes and has stimulatory effect on plant growth.

 

Weeding

One of the causes of poor farm harvest is weed. Yam cannot withstand the effect of weed.

Yam farm should be regularly weeded at least 2-3 times before harvest.

During weeding, build up the ridge from the soil in the furrow from bottom to top. This will prevent the ridge from being reduced in size by erosion during the rainy season. This practice is called earthen-up.

 

Pest and Disease Management

Ø  Plant yam varieties that are resistant to anthracnose.

Ø  Use disease free tubers or setts for planting.

Ø  Keep the farm free of weeds.

Ø  Termites attack is controlled with neem leaves and oil.

Ø  Destroy crop debris on the farm.

Ø  Treat tubers with hot water for 40 minutes at 55^OC before sowing and after harvest so as to reduce disease while in the field and after harvest.

Ø  Coat tubers with wood ash to prevent nematode infestation.

Ø  Practice crop rotation with groundnut, sorghum, maize or chili pepper.

Ø  Neem oil insecticide is applied to kill all stages of mealy bug infestation.

 

Harvesting

Harvest the yams when the leaves starts turning yellow.

Dig the soil around the tubers to avoid damaging the tubers.

Harvesting is best done on a dry or sunny day to avoid tuber rot.