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Sweet Potato: Cultivated Area and Production

Sweet potato plays an essential role in the tropics as a food security crop because of its (i) relative tolerance to water stress, (ii) dual utilization, either for human consumption or animal feed, (iii) high nutritional value, i.e., high content of carbohydrates, protein, minerals, and vitamins, (iv) relatively short growing season, and (v) adaptation to a wide range of environmental conditions.
Worldwide, the area with sweet potato spread between 40 degrees north and south of the equator and from the sea level up to 2300 m or higher. Within this latitudinal belt, the cultivated area in 1991 amounted to 9.3 million ha, of which 2.6 million ha were located in the tropics, specifically 1.3 million ha in tropical Africa. The world production, in turn, amounted to 126 million metric tons (MT), of which only 15 million MT were produced in the tropics. China was the major producer, with 6.4 million ha and a production of 107 million MT, followed by Uganda with 0.4 million ha and 1.8 million MT. Except for maize and bananas, which are cultivated in 119 countries, sweet potato is cultivated in more countries (100) worldwide than any other food crop. Yet, except for few commercial operations, sweet potato production in the tropics is generally characterized for subsistence technology and concomitant low productivity. Compared with average yields obtained in temperate zones (i.e., 21 Mg/ha in Japan), the average yield is below 6 Mg/ha in all tropical regions except Asia (15 Mg/ha). From an economic standpoint, sweet potato ranks quite below other crops with a farm price of 8 cents/kg compared with 30, 17, 15, and 14 cents/kg for unshelled peanuts, rice, wheat, and potato.
Africa
Kenya. Sweet potato is an important crop in Kenya with a cultivated area in 1990 of 57,000 ha. Fifty five percent of the production area was concentrated in the Nyanza and Eastern regions with South Nyanza, in southwestern Kenya on the shore of Lake Victoria, as the main production area. Overall, subsistence technology prevails in most production areas with yields below 7 Mg/ha in all but the Nyanza and Coast provinces.
Uganda. Sweet potato is extensively cultivated in Uganda with a cultivated area of 412,000 ha and an annual production of 1.7 million MT. Root yields are as low as 4 Mg/ha, as production takes place mostly in subsistence systems using indigenous cultivars, with no application of inputs or technology, and besieged by diseases and pests.
Rwanda. Sweet potato is widely cultivated year-round in Rwanda with a cultivated area of 147,000 ha and an annual production of 817,000 MT. Major production areas in the country include Butare, Ruhengeri, Gikongoro, and Gitarama where the crop is grown up to 2300 m in elevation, sole or in mixed stands with beans, sorghum, or cassava.
Ethiopia. Sweet potato is one of the major root crops in Ethiopia with some 18,000 ha located in the east, south, and west. Average root yields are quite low (8 Mg/ha) partly due to inadequate technology, diseases and pests, and low yielding cultivars.
Sri Lanka.From a food standpoint, sweet potato and cassava are important crops in Sri Lanka, a country with endemic calorie deficiency and besieged by growing population and land shortage. Yet the cultivated area is quite small (17,770 ha with an annual production of 135,000 MT) and low productivity (8 Mg/ha).
Central America and the Caribbean Basin
Despite that local environmental conditions are ideal, sweet potato is not an important crop in Central America and the Caribbean. Little research has been conducted on either agronomic management or cultivar evaluation. In addition to spare research, marketing, that is lack of marketing is probably the most limiting factor in the region. Yet, the crop is frequently cultivated for home consumption in small gardens and less frequently as a cash crop in small areas near large cities.
Barbados. Sweet potato production is a marginal activity in Barbados. The crop is grown in relay or intercropping systems with sugarcane and the local production has declined from 5700 MT in 1970 to 3000 MT in 1981. Several factors such as (i) lack of demand for sweet potato, (ii) changes in rainfall patterns, (iii) unfavorable market prices and poor storage conditions, and (iv) declining sugarcane production have contributed to this production decline.
Dominican Republic. Sweet potato is an important crop in this small country. But production has considerably declined from about 128,096 MT in 1973 to 63,280 MT in 1980 partly due to the low social status of the crop, lack of technology and high yielding cultivars, and a general state of stagnation of the local agriculture.
South America
Brazil. Brazil is the leading producer in South America with a cultivated area of 68,000 ha and an annual production of 683,000 MT. Production in this country is concentrated on the subhumid tropical lowlands of the northeast and the subtropical lands of the south.
Chile. Historically, sweet potato has been an important food in Chile. In the past, sweet potato was part of pre-Colombian cropping systems that included maize, pumpkin, chili, and other local crops. Presently, sweet potato is grown during the spring and summer months as temperatures are suitable for plant growth. Yet the cultivated area has steadily declined from 155,000 ha in 1955 to 56,000 ha in 1991.
Guyana. After cassava, sweet potato is probably the second largest root crop in Guyana. The crop is found intercropped with perennials such as coffee, citrus, and avocado where it is generally planted simultaneously with tree seedlings and harvested as trees begin to cover the ground.
Asia
India. India has a long history of sweet potato cultivation. It is presently cultivated in about 160,000 ha with plantings in the Bihar and Uttar Pradesh areas accounting for 60% of the total area. In the Bihar area alone, 51,390 ha are cultivated with an annual production of 3.5 lakh tonnes. Sweet potato is the third most-produced crop after potato and cassava and government prospects is to cultivate about 0.5 million ha by the year 2000.
China. Sweet potato ranks fourth in China after rice, wheat and maize. The cultivated area in 1990 was about 6.3 million ha with an annual production of 10.4 million MT. The main production areas are located in the Yellow (40%) and Yangtze River (30%) basins. Although mainly consumed as a food, sweet potato roots have been increasingly used as a raw product for animal feed and industrial biproducts.
Bangladesh.Bangladesh is one of the major sweet potato producers in the world with a cultivated area of 52,000 ha and an annual production of 538,000 MT. The crop is often grown on a commercial scale but mostly as a component of subsistence systems. Overall, sweet potato is a neglected crop grown in marginal lands without agricultural inputs and technology and using local low yielding cultivars.
Philippines. Cassava and sweet potato are the most important root crops in the Philippines, particularly in eastern Visayas and Bicol. The cultivated area in 1990 was 136,685 ha with an annual production of 668,875 MT. Yields are quite low (5 Mg/ha) as the crop is grown in small patches (85% of the patches are less than one ha) on gently sloping lands with little crop husbandry. Ninety five percent of the production is consumed as food and the rest is used as animal feed and waste.
Indonesia. Sweet potato is an important crop in Indonesia with a cultivated area of 232,000 ha and an annual production of 2.1 million MT. Java is the most important production center, with about one million MT produced in almost one half of the cultivated area, followed by Sumatra, Irian Jaya, Maluku, and Nusa Tenggara.
Vietnam. The area planted with sweet potato in Vietnam has declined from 450,000 ha in 1980 to 328,000 ha in 1990. In South Vietnam, sweet potato is mainly grown in the north while in North Vietnam, 50% of the cultivated area is concentrated in the region from Thanh Hoa to Thua Thien in the north and central coastal zone. The crop is mainly grown in marginal soils using subsistence technology which partially accounts for the low productivity, 5 to 7 Mg/ha.
Thailand. Sweet potato has always been a minor crop in Thailand. Lately the crop is being grown commercially with a cultivated area of 40,000 ha and an annual production of 355,000 MT, mostly in the center of the country (36%) followed by the south (27%), north-east(27%) and the north (10%).
Taiwan. With a cultivated area of 230,000 ha, sweet potato in Taiwan has been the most important crop after rice for about 25 years since 1948. Lately, however, production has consistently declined partly due to the increasing use of maize as animal feed and also because of expanding water resources for rice cultivation. Currently sweet potato is grown in rice-based cropping systems with tobacco, sugarcane, legumes, and vegetables.
South Korea. Sweet potato is the third most important summer crop in South Korea after rice and barley. But in recent years, both planted area and production have declined from 127,000 ha in 1970 to about 37,000 in 1985 with 2.1 million MT in 1970 to 0.9 million MT in 1985. Limited storage facilites, lack of postharvest technology, and the crop's low profit are the main reasons for the productivity decline.
Pacific Basin
Papua New Guinea (PNG). In 1963, the estimated annual production in PNG was about 1.2 million MT from an approximate area of 72,000 ha. Since then the production has increased to 460,000 MT with a cultivated area of 101,000 ha. Either sole in the highlands or intercropped with cash crops and vegetables in the lowlands, the crop is grown in a wide range of environments, from the sea level up to 2000 or 2800 m in elevation in rainfall regimes from 1000 to 8000 mm.

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