Yam (vegetable) - Production

Production

Yams are farmed on about 5 million hectares in about 47 countries in tropical and subtropical regions of the world.

Yam crop begins when whole seed tubers or tuber portions are planted into mounds or ridges, at the beginning of the rainy season. The crop yield depends on how and where the setts are planted, sizes of mounds, interplant spacing, provision of stakes for the resultant plants, yam species, and tuber sizes desired at harvest. Small-scale farmers in West and Central Africa often intercrop yams with cereals and vegetables. The seed yams are perishable and bulky to transport. Farmers who do not buy new seed yams, usually set aside up to 30 percent of their harvest for planting the next year. Yam crops face pressure from a range of insect pests, fungal and viral diseases, as well as nematodes.

Yam typically grows for six to ten months and is dormant for two to four months, depending on the species. The growth and dormant phases correspond respectively to the wet season and the dry season. For maximum yield the yam requires a humid tropical environment, with an annual rainfall of over 1500 millimeters distributed uniformly throughout the growing season. White, yellow and water yams typically produce a single large tuber per year, generally weighing 5 to 10 kilograms.

Yam production requires high labor. The crop has low yield per hectare compared to crops such as cassava (manioc) or sweet potato. It is not an efficient food staple given the relatively large amount of planting material that is required and its long growing season. Yam's labour requirement exceeds that of other comparable crops. Yam is also difficult to preserve and store over extended periods of time. The cost per 1,000 calories of yam is four times greater than those of other root and tuber crops.

For these reasons and problems of storing harvested yam, the costs of yam production are high and yam crops are slowly losing ground to cassava and other food staples.

Despite these high costs and low nutrient density, when compared to other tubers and roots, low technology yam farming produces the highest amount of food calorie and protein annually per hectare per season, on average. Given this nutritional value of yam and its high cultural acceptance in certain parts of Africa, there is an interest in developing knowledge that can improve yam agriculture.

In 2010, the world harvested 48.7 million tonnes of yam, 95 percent of which was produced in Africa. The biggest yam harvest, globally, was in 2008, when the world produced 54 million metric tonnes of yam.

The world average annual yield of yams was 10.2 tonnes per hectare in 2010. The most productive yam farms in the world were in Colombia, where nationwide average annual yield was 28.3 tonnes per hectare. These are average national yields; certain farms report yields significantly above 30 tonnes per hectare, for example for yellow yam; other farms report yields less than 1 tonnes per hectare.

Despite the high labor requirements and production costs, consumer demand for yam is very high in certain subregions of Africa, making yam cultivation quite profitable to certain farmers.