Blackberries prefer a deep, well drained, organic rich soil. They are difficult to grow in heavy soils, because they are susceptible to root rot and iron chlorosis. They must have adequate drainage.
Before planting, add a two to three-inch layer of organic matter to the soil and till 12" deep - especially when working with heavy clay soils. The organic matter will loosen and lighten soil texture, increase drainage in clay soils, help hold moisture in sandy soils, and reduce alkalinity. Apply 4 to 8 cups of nitrogen fertilizer (21-0-0 analysis) per 100 square feet to help break down the organic material.
Plant dormant plants to 6" stubs and set them at the level where they grew in the nursery and from 4' to 8' apart. Rows should be 6' to 9' apart.