Planters can be equipped with rolling coulters that are 18 inches in diameter or larger. Whether the coulters are fluted, rippled, notched, or smooth, they must be sharp, weighted or spring pressured, and set deep enough to cut cleanly through the stubble without punching it into the furrow. Straw mixed into the soil above the seed may cause corkscrewing of the seedlings. See G83-684, Row Crop Planters , for a detailed discussion on equipment, adjustment and performance in conservation tillage. Coulters should be rust-free and sharpened with a disk roller.
Smooth coulters give the best performance for stubble cutting.
Fluted coulters provide more loose soil for better seed coverage. However, they do not scour properly when the soil is wet and they do not cut straw adequately if stubble is damp. Wide fluted coulters throw straw away from the row better than narrow fluted coulters, but require more weight for penetration. They also disturb the herbicide barrier more. By removing straw from the row, soil warms up faster, an advantage when soils are cold.