Imagine this: It’s one of the oldest vegetable known with potential yield between 20 and 50 tonnes per hectare. To compare, the average yield of maize per hectare in Kenya is about 1.6 tonnes (global yield of maize is 12 tonnes/Ha).
Oh wait. Unlike maize that requires a lot of water and fertiliser, the sweet potato is drought resistant and it can grow in any part of this country. In fact, it’s grown extensively in Western and Nyanza, Rift Valley, Coastal and Central Kenya although yields remain low. As a crop cover, it suppresses weeds, controls soil erosion and improves soil fertility through nitrogen fixation and humus deposition.
It is tasty, nutritious, has high levels of beta-carotene, vitamins E, C and it contains moderate levels of potassium, iron and vitamin B6. The tuber, vine, and leaves are used as human and livestock feed.
Aha, there are multiple ways of preparation. It can be eaten boiled, roasted, baked, or grilled; mashed, chipped or noodled. Its juice is used for weaning. The flour can be used for baking bread and cakes, in baby food formulas and as an industrial starch.
The sweet potato (Ipomoea batatas) was first cultivated in the South and Central America from where it spread to the rest of the world. It’s not related in any way to the famous white (Irish) potato. The latter sprouts from buds (eyes) within the tuber while the former is propagated from vines.
In sub-Saharan Africa, the tuber is grown on 2.1 million hectares and yields 9.9 million tonnes of tubers (FAOSTAT, 2009)—averaging 10 tonnes per hectare. China, which is responsible for 80 per cent of the global supply of this tuber produces 70,526,000 tonnes per year. In Africa, Nigeria and Tanzania—the leading producers in the continent—produce 3,689,700 and 3,470,300 tonnes, respectively. Kenya is at position 20.
To improve productivity, researchers have developed new varieties for different ecological zones. These include Kemb 10, SPK 004, KSP 20, KSP 11, CIP, 420009 for dry areas; SPK 013 for the Western zone including the Lake Basin; Kemb 23 and Ex-Diani are suitable for Central and Coastal lowlands; while Mafuta is suitable for all sweet potato producing areas and is best for foliage production.
These varieties come in skin and flesh colours that range from white to yellow, orange, and deep purple, some of which are used to manufacture dyes. In fact, if you want to get yellow-yolked eggs, feed your chicken orange-fleshed sweet potatoes.
Together with cassava, sorghum, millet and green grams, the sweet potato is categorised as an orphan crop reserved for the poor although it’s a potential export crop.
Muriuki is an agricultural expert and consultant with Crest Agricultural Consultants Limited