Gardening Articles: Care :: Soil, Water, & Fertilizer
Planting Sweet Potatoes
by National Gardening Association Editors
The roots of sweet potatoes need to swell and expand easily; therefore, the slips are usually planted in raised rows ranging from 6 to 10 inches high and from 2 to 3 feet wide. Raising the soil in hills or "ridges" is especially important with clay soil. Heavy soils tend to compact, which restricts the underground growth of the roots and sometimes resulting in rough, odd-shaped potatoes. Heavy soils also tend to drain poorly.
Just as with white potatoes, you can improve heavy problem soils for better sweet potatoes by mixing in plenty of organic matter such as leaves, grass clippings, hay, compost or peanut hulls whenever and wherever you can.
You can prepare your ridges a week or so before planting, while the indoor-grown slips are hardening off or when your bedded slips reach 6 to 9 inches in height. Till or spade the soil first, working crop residues into the soil, making it as loose as possible. The soil pH should be in the 5.6 to 6.5 range, slightly on the acid side. As soil pH nears 7.0 (neutral), sweet potato plants become more susceptible to certain diseases.
Stake out your sweet potato rows, allowing about three feet between them so you can walk between the rows to weed or cultivate. Use a hoe to draw up the tilled, loose soil and form a fairly level planting bed. You can easily smooth out the ridges with a rake before planting the slips.
Sweet potato plants gobble up a lot of nutrients from the soil to feed their burgeoning roots and extensive vines, which for some varieties may reach 15 to 20 feet in a long growing season.
Fertilizing is a delicate matter, too much plant food -- especially nitrogen -- will produce skinny potatoes. With too much nitrogen, the vine portion of the plant dominates the growth, and root formation is delayed. But with too little fertilizer, the harvest won't meet your expectations.
When using commercial fertilizer, the basic guideline is about four to five pounds of 5-10-10 for each 100-foot-row. If your soil is fairly fertile, you can cut this recommendation to two or three pounds for each 100-foot-row.
The simplest way to apply the fertilizer is to broadcast it before making your ridges. Spread it uniformly over the row and include some of the soil area you will use for building your ridge.