Deep banding refers to preplant applications of nutrients placed 2 to 6 inches below the soil surface. Some applications are deeper, as much as 15 inches. The applied nutrients may be in solid, fluid, or gaseous forms. Concentrated zones of nutrients are produced, either streams sheets or points, depending on the design of the applicator. In some areas this fertilisation technique is performed many months before the next crop is seeded, often in conjunction with a tillage operation.