Botanically speaking, the underground part of the sweet potato (Ipomoea batatas L.) is classified as a storage root, rather than a tuber, as is the white (Irish) potato (Solanum tuberosum).
Site selection and planting
Sweet potatoes should not be grown on the same land more often than once every 3 years. Farmers should avoid fields with a history of difficult to control perennial weeds. Sweet potatoes do best on light, deep, friable loams (sandy loam) with high fertility. Propagation results from vine cuttings, which are referred to as “slips”. Ten to 12 bushels of disease-free sweet potatoes should be bedded to produce enough slips for one acre.
Sweet potatoes are usually bedded about 7 weeks before field setting time. Sweet potatoes are cold-sensitive. Providing an even supply of water during the first 40 days after planting is especially important for quality root development. An uneven water supply can result in growth cracks; drought conditions may reduce yields; and excess moisture may injure roots. Additionally, watering during this critical period can help plants survive water-related stresses later on.
The main insect pests are those that feed on the roots, such as wireworms, flea beetle larvae, and sweet potato weevils. Diseases include black rot and scurf, Fusarium wilt, root knot nematodes, and post-harvest rots. Resistant cultivars, crop rotations, sanitation, and weed management are important tools in disease and insect management.
Harvest and post-harvest handling
Sweet potatoes should be harvested once they reach the weigh of at least 300grams. A good practice is to clip the vines before harvesting so they do not get in the way during harvest, resulting in less damage to the potatoes. A turn plough can be used to expose the roots with the least possible injury. Potatoes are graded in the field and then placed in containers that are to be put into storage.
Following harvest, sweet potatoes need to undergo a curing process to promote the healing of wounds (for example, from digging). Curing protects roots from many storage diseases and increases the post-storage lifetime of the root. Additionally, curing improves root flavour and texture. Curing is best accomplished at a temperature of 30°C and relative humidity of 80% to 90%. After curing, sweet potatoes may be stored for 4 to 7 months under the proper conditions, including ventilation. Sweet potatoes are cleaned, either by brushing or washing, and then sometimes waxed before packing into boxes, crates or baskets for market.