Soil Preference

Soil PH: 4.5-7.0, Ideal 5.5-6.5

The Sweet Potato does better in poor soils than most other crops, but (as is usually the case) better soil will give you a larger crop. The ideal soil for Sweet Potatoes is a rich, deep, well-drained sandy loam that retains moisture. It should be fairly acidic, as this reduces disease problems. If the soil is poorly drained there is a risk of root rot. Heavy clay soil isn't good as it may produce slender roots.

Soil Preparation

Standard Mix, 5 pound(s) per 100 sq. ft., in top 8in of soil, 1 time

Like most root crops, Sweet Potatoes need plenty of phosphorus and potassium, but not a lot of nitrogen, which encourages the growth of foliage rather than roots (and can even result in inferior roots). Incorporate 5 lbs. of Standard Mix into your soil to provide them with these nutrients.

Compost (N), 3 inch(es), in top 8in of soil, 1 time

Sweet Potatoes like organic matter and compost will be beneficial no matter what type of soil you have. It will help to lighten a heavy clay soil, help a sandy one retain moisture and supply nutrients in all situations.

If your soil is heavy or compacted it is a good idea to loosen it by double digging and adding plenty of organic matter (or you could build raised beds and import soil).