Botanically sweetpotato or Spanish potato is called Ipomoea batatas (L.) Lam, belongs to the morning glory family (Convolvulaceae) and originated from Latin America. Sweetpotato ranks as the world’s seventh most important food crop, after wheat, rice, maize, potato, barley and cassava. More than 133 million tonnes are produced globally per year. Uganda is the main sweetpotato-growing country in Africa (Anon. 2002), with production of over 2.7 million tonnes, mostly for human consumption and the second leading producer after China at 117 metric tonnes globally (FAO 2003). Historically, sweetpotato has been a lifesaving disaster crop, for example the Japanese have used it when typhoons demolished their rice fields, it kept millions from starvation in famine-plagued China in the early 1960sand in Uganda, when a virus ravaged cassava crops in the 1990s, rural communities depended on sweetpotato to keep hunger at bay. Sweetpotato is high in carbohydrates and vitamin A and can produce more edible energy per hectare per day than wheat, rice or cassava. It has an abundance of uses, ranging from consumption of fresh roots or leaves to processing into animal feed, starch, flour, candy and alcohol. The crop can be grown in poor soils with little fertilizer and has hardy nature and broad adaptability.
Although Uganda is the second largest producer of sweetpotato after China, farmers still realize low yields, averaging only 4,500 kg per hectare (1800 kg per acre) compared to 30,000 kg per hectare (12,000 kg per acre) obtained on research stations. The wide yield gap is due to a number of reasons, including a) use of local varieties with low yield potential, b) pests and diseases, c) shortage of planting materials, d) non-availability of improved varieties, and e) poor crop husbandry practices such as poor seed bed preparation, low or high plant population, late planting, late weeding and poor soil fertility management.