Revised May 2008 by Diane Huntrods, AgMRC, Iowa State University.
Background
The sweet potato (Ipomoea batatas) is a native American plant found by Columbus and his shipmates, probably from the West Indies islands off the coast of Yucatan and Honduras. In colonial days, George Washington grew sweet potatoes on his Virginia farm. Years later, George Washington Carver developed over 100 different products from sweet potatoes, including an alternative to corn syrup. During World War I, the USDA used sweet potato flour to stretch wheat flour in baked goods.
Despite its name, the sweet potato is not related to the potato. Sweet potatoes belong to the morning glory family, while potatoes are members of the Solanaceae family, which also includes tomatoes, red peppers and eggplant.
Despite a physical similarity, sweet potatoes and yams are not related either. Yams are actually related to grasses and lilies. Most yams marketed in the United States are sweet potatoes with a relatively moist texture and orange flesh. The native sweet potato is dry fleshed and pale yellow. When producers and shippers began growing orange-fleshed sweet potatoes in the southern United States, they needed to distinguish them from the lighter fleshed types. Although “sweet potato” and “yam” are generally used interchangeably, the USDA requires that sweet potatoes labeled “yam” always be accompanied by “sweet potato” to differentiate them from true yams.
Value-added Products
Widely established throughout the world, the sweet potato is a favorite staple of many cultures and is an ingredient in many ethnic cuisines. In the northern United States, the sweet potato is used only as human food. In the southern United States, it is far more extensively used in regional cuisines, and a large part of the crop is fed to livestock. Efforts are being made to breed varieties that will inexpensively produce large yields, so that they can be grown specifically for feed or industrial applications.
In developing countries, sweet potatoes are grown mainly as a substitute for rice and corn. There, sweet potatoes rank as the fifth most important food crop on a fresh-weight basis, after rice, wheat, corn and cassava. However, sweet potatoes use has diversified considerably over the last four decades, having great potential as a source of local value-added products and ingredients. Some examples include food products like noodles and desserts; animal feed; and some industrial products such as flour, starch and pectin for local and export markets.
In Africa and Asia, dried sweet potato is used as a substitute for yellow corn animal feeds. For instance, the steady increase in the use of sweet potato roots and vines for pigs and other livestock in China during the last 30 years means that from 30 to 50 million tons or more are used annually as feed. Sweet potato flour can be fermented to make products like soy sauce and alcohol, or if immediately cooked, it can be further processed into wine, vinegar and nata de coco, or “on-the-go,” a dessert popular in the Phillipines and in Japan.
The sweet potato generally contains more starch than the potato, and the starch has properties that are especially useful in many food products and manufacturing processes. At this time, however, the growing and handling of the crop is too costly for it to be produced just for starch production. In China, however, production of sweet potato starch in recent years has evolved into a cottage industry that uses millions of tons of roots per year.
Unprocessed sweet potatoes do not have an extremely long shelf life compared to other vegetables like carrots or potatoes. For this reason, drying, freezing or processing sweet potatoes into a frozen prepared food may benefit producers or processors by extending shelf life and gaining increased market visibility.
Production
Most sweet potato production is in the southern United States, namely, North Carolina, Mississippi and Louisiana. California is also a significant producer. The estimated farm value of the 2007 U.S. sweet potato crop jumped 27 percent to $374 million--well above both a year earlier and the 2003 record-high crop value. In 2006 per person consumption in the United States was 4.6 pounds, up 2 percent from the preceding year but down from the recorded high of 13.9 pounds in 1949. The Beauregard is the dominant sweet potato variety grown. Other varieties include the Hernandez, Jewel, Garnet (red-skinned) and Golden Sweets (yellow to white fleshed) varieties.
With respect to North Carolina, the top producing state, stronger prices boosted the value of the state's 2007 crop 30 percent to $148 million—the highest on record. It is estimated that more than 70 percent of commercially grown product in North Carolina is directly sold into one of three outlets: chain stores, terminal market facilities or foodservice providers. The remaining 30 percent is sold to processors for canning, flaking, chipping, frying, freezing or baby food.
California sweet potatoes’ exceptionally high yield and above-average prices account for a good portion of the growth in U.S. crop value per acre. The California crop, however, has the disadvantage of a shorter shelf life (does not store as well) relative to sweet potatoes produced in other states.
China is, by far, the world’s leading producer of sweet potatoes and accounted for 82 percent of global sweet potato production in 2005. The United States produced less than 1 percent of the total 122 million metric tons harvested around the world that year.
Marketing
The North Carolina Sweet Potato Commission (NCSPC) suggests that growers develop a marketing plan well in advance of entering this market. The NCSPC recognizes that successful marketing is a challenge for most growers.
One requirement is that growers deliver high-quality sweet potatoes to the correct locations, at the times and in the forms that buyers want them. The NCSPC found that inexperienced growers tend to provide a product of variable quality over shorter time periods than more experienced growers. Therefore, they are more limited in their marketing opportunities and more directly impacted by current sale prices. Factors that significantly influence price and marketing options for individual operators include local and national supply levels, and production and transportation costs relative to competing growers. These factors could prompt a decision to market locally or to sell to an agent or broker.
Most medium- to large-volume producers employ a sales agent. The agent has sole responsibility to locate and contact buyers and to arrange transportation. The sales agent works exclusively for the farmer-shipper and negotiates with the buyer over the time and place of delivery, the quantity to be sold and the price.
Some growers hire a broker, who negotiates the specific details of a sales contract between a seller and buyer. Brokers will work for a seller or buyer (depending on who is paying the brokerage fee). They seldom, if ever, take possession or handle the product.
For small-volume producers, marketing options may include direct sales to consumers and selling to local grocery stores or local shipper-packers. In several areas of North Carolina, growers have organized marketing cooperatives that permit them to cooperatively market and perhaps transport product. With the increased volume, they are able to hire their own full-time sales agent to handle sales and new market development.
Export and Import
Nearly 6 percent of domestic production is exported. The value of fresh and frozen sweet potato exports rose 33 percent to $32 million, recouping the decline experienced in 2005. Much of the gain resulted from the 63 percent jump in the value of shipments to the United Kingdom (UK). Canada and the UK remained the two top foreign markets for U.S. sweet potatoes in 2006, with 61 and 29 percent, respectively, of export value.
The value of U.S. fresh and frozen sweet potato imports rose 24 percent to $5.5 million. The Dominican Republic remained the largest foreign source of fresh and frozen sweet potatoes, with 84 percent of the 2006 U.S. import market.
Outlook
One development that can push demand for U.S. sweet potatoes to a higher level is the success of Evangeline, a new sweet potato variety. Louisiana State University researchers developed this variety, which contains 30 to 50 percent more sugar than the popular Beauregard. The variety's appeal to consumers may be further enhanced by a more consistent shape and a darker orange flesh.
Demand for U.S. sweet potatoes improved in 2006 as evidenced by larger exports, rising per person use and higher prices despite a larger crop. These gains are expected to continue, as exports expand at a double-digit pace and domestic use remains strong. Long-term expectations are for producers to increase their acreage to satisfy the increasing demands of more health-conscious consumers and to take advantage of niche markets to increase profitability.
Profile created May 2004 and revised May 2008.