| B6, and manganese, as well as a small amount of potassium. Surprisingly acre per acre, sweet potatoes have twice the food value as does rice. Although sweet potatoes and yams look alike, the yam is from a subtropical shrub that is native to Africa, while the sweet potato is from the American morning glory family.
Sweet potatoes are not grown from seeds, but rather from transplants or vine cuttings. Transplants (12" to 18" sections) are also called slips and are grown from mother roots (seed potatoes). Sweet potatoes are planted after the danger of frost. Where irrigation is available, good yields may be obtained in plantings made as late as the last of June.
Sweet potatoes do best in well-drained sandy loam soils relatively low in nitrogen. Excessive nitrogen or heavy applications of animal manures can cause long spindly roots and low quality. Heavy soils cause misshapen roots. Light loamy soils usually result in roots with better shapes. Coarse, deep, sandy soils are generally low in fertility, subject to moisture stress and require more irrigation and fertilizer to grow a good crop. The soil pH should be 5.0 to 6.0.
To prepare the soil, rototill or fork in a 2-inch thick layer of compost and plenty of bone meal. Apply 8-8-8 fertilizer at the rate of 2 lb. per 25 feet of row. Push the softened, fertilized soil into a foot-wide flat-topped ridge row that is 8 inches high.
Transplants should be set deep, with at least three nodes (joints where leaves are attached to transplants) below ground level. Increasing planting depths up to five nodes has been shown to increase yields.
Planting the slips in a deep trench and ‘hilling up’ the soil as the plants grow will increase yields dramatically. Be sure to keep at least 12 inches of the plant foliage exposed above the soil as you periodically hill it up.
Maintain as many healthy leaves as possible on the transplants. Healthy leaves are required for food synthesis, which hastens root development and early establishment of the plant. Removing the lower leaves during transplanting reduces yields as much as 20 percent. Likewise yields can be increased dramatically by transplanting only strong, stocky slips like those found at your local Co-op store.
Water the plants with a starter solution such as 10-34-0. The high phosphorus content of the solution enhances early root development and growth, and the liquid settles the soil and eliminates air pockets. Thirty days after transplanting, sidedress with 8-8-8 fertilizer again at the same rate (2 lb. per 25 feet of row).
Avoid disturbing the roots with foot traffic or deep hoeing. Water thoroughly about every 7-10 days.
Sweet potatoes require very little care. A bit of weeding, done carefully so as not to injure the shallow roots is usually all that is needed. Yield losses to weeds are often less obvious than losses from insects and diseases because weeds do not have the definite symptoms that diseases and insects do. Weed competition for moisture and nutrients reduces plant vigor, food manufacturing surface and yield, so make every effort to control all weeds throughout the growing season.
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