The usual range of available opener spacings is from 6 to 8 inches, which is the conventional spacing for wheat. Some farmers double-drill forages in two directions for a closer effective spacing. A few drills are available with spacing down to 4 inches for high-yield wheat. This is a desirable spacing for forage, but presents problems in spacing no-till coulters. To get close spacing with planters and drills, the openers usually must be staggered by mounting on two or more parallel bars.
Most drills used in the more humid eastern United States have double-disk openers.
Drills with hoe, shovel or knife-type openers penetrate hard soil well, but tend to operate at varying depths and to rake trash. The opposing disk may be set back an inch or so and completes opening the furrow. Operating without a no-till coulter to cut residue and open the hard ground may cause disks to wear down sooner and make bearing life shorter. There are, of course, fewer components to buy or replace. Things to look for Weight.