A few drills are available with gauge wheels alongside the opener, resulting in more accurate depth control under most conditions. Depth bands probably give the most precise depth control. Disadvantages of depth bands include high cost, difficulty in changing depth and poor operating in wet, sticky soil. On some drills, operating depth varies to some extent with the weight on the drill. Some drills are too heavy to operate well in tilled soil.
Drills frequently change depth as the soil changes from dry to moist or from clay to loam.
Press wheels and seed covering. Many sizes and configurations are available for most drills, from a narrow, single press wheel to two wheels in a Vee configuration. Materials range from zero-pressure rubber tires to hard rubber or steel. The double-Vee configuration is popular for operation in a wide variety of tillage conditions. A wide press wheel that is effective in loose, tilled soil usually is not effective in no-till unless it has ribs about 2 inches apart to create down pressure near the seed furrow.