Many of these do not require any modification. Planter performance is influenced by planter features and attachments, as well as proper machine adjustment and operation. While options are available for adapting planters to a wide variety of soil and residue conditions, major features are largely dependent on the brand of planter. Commonly available seed furrow openers are illustrated in Figure 2 . The major function of seed furrow openers is to create a well-defined groove in the soil where the seed can be placed at the proper depth.
Research indicates no difference in seed spacing uniformity exists among the various openers.
Although a runner can create a cleaner seed furrow, the double-disk opener can cut through residue and reduce potential clogging problems. The double-disk opener also has better depth control under conservation tillage conditions because, unlike a runner, it does not have a tendency to float up and over residue. With this design, the leading edge of one disk is slightly in front of the other. The leading disk cuts the residue and soil and the trailing disk helps open the seed furrow. A variation of a runner opener is a slot shoe opener which slides under the residue and lifts it out of the seed furrow.