YAM is an important food crop grown in Malaysia and other tropical regions.
It is considered the chief source of calories for many communities in the continents of Africa, Asia and South America, as well as those in the islands across the Caribbean and the South Pacific.
The plant is an herbaceous crop from the Dioscoreaceae family, producing tubers in various colours. Scientifically known as Dioscorea spp, it originated in South Africa from which many cultivars and species, each with its own taste and colour, are derived.
Taro (Colocasia esculenta L) is a tropical plant grown primarily for its edible corms, viable for backyard and commercial planting. The corm is the most important commercial part of this plant and its wide leaves resemble elephant’s ears. Of the 200 off-cultivars, there are two main groups: the wetland taro, which is a staple for many Polynesian communities; and the upland taro, which produces eddoes meant for cooking and other food products.
Planting taro uses the setts from the suckers of the main plant. This tuber can grow in a wide range of soil types – in heavy clay loams with high water-holding capacity and organic matters.
Potassium is important for starch formation.
The local favourite is the ‘pinang yam’ or the Chinese yam, mostly distinguishable by the size and the texture of the carbohydrate-filled content, making them suitable for various methods of cooking such as frying, baking and boiling.
The famous yam rice in Penang has it mixed with a variety of ingredients, while many Chinese recipes include it being made into many types of cakes and dumplings.
My friend, Wong, grows pinang yams in polystyle boxes at home after having searched for this fragrant variety in and around Kuching – his daughter incorporates this yam in many baked goods.
Pinang yam is pricey – it is now between RM15 and RM18 per kilogramme.
The largest yam production region is West Africa, with Nigeria being the top producer.
There are at least six species of yams grown there, including the pinang yam.
When I visited Nigeria in the 1980s, we were served with ‘coco-yam’, a staple food there, and what I could say was it was not palatable – at least to us.
In China, pinang yam is grown on the borders of paddy fields. Such condition provides the crop with sufficient water for good harvest.
In Thailand, yams are grown in beds with irrigation channels in between for good water supply and transportation.
Why so expensive
There are actually several reasons, one of which the higher cost of input, fertilisers and chemicals (pesticides). The horticultural requirements for growing pinang yam include suitable land and favourable weather conditions.
Pinang yam requires a long gestation period. Some take about eight to 12 months to be ready for harvest. Small farmers find it non-economical to occupy precious land areas for other shorter seasonal/annual vegetables or food crops.
Next, the yam plant is subject to several diseases, including those caused by fungus and bacteria that could result in the corms rotting away.
Anthracnose (fungal diseases that typically cause dark lesions on or rotting in leaves) can reduce starch production.
The crop needs mulching and continuous removal of suckers spreading out from the base, in order to enable generation of new plantlets outside the mother yam.
These suckers need to be removed to avoid them consuming the energy that should go into nourishing the corm.
The target is to grow a good, healthy corm – the bigger, the better.
There are several cultivars in the market, with some having small corms and some having lost its fragrance. The well-versed consumers would select the right choice by cutting the end of the corm to see the right colour and pattern of the distinguishing ticks and dots inside. The imported ones from Thailand have large corms but are without any pleasant smell; some of those imported from China have no aroma at all.
Nutrition-wise, these tubers are packed with carbohydrates, fat, protein and vitamins B, C, E and K, Folate B, as well as mineral that include magnesium, iron, calcium and manganese.
Cultivation and propagation
Propagation is by using the setts (over the section just above the bulb or the corm, together the shoot end).
To speed up the sprouting of roots, we can insert the plant in shallow-depth water containers – change the water now and then to avoid rotting.
It can be directly inserted in the nurseries or barn-rows before field planting.
The easy way of propagation is to take the suckers from the mother plant for direct field-planting.
The preferred soil is rich, red loamy variety that promotes well-drained conditions.
The soil should be sandy, but not ‘clayey’. The pH range is from 5.5 to 7.0.
During growth period, it needs distributive rainfall, humid and warm weather with sunlight. Any foliage disease due to fungus or pest attack can be addressed by using pesticides.
The worst condition for yam-planting is waterlogging, which can rot the corms and render it hard.
Well, I hope those of you interested in growing pinang yam can try it now, using the tips given here.