The fully enclosed convex press wheels are the best except in moist clay soils, where the semi-pneumatic are preferred because they pick up less moist soil. The press wheels help cover the seed with soil and prevent premature drying of the seedbed, as well as good soil-seed contact for fast germination and therefore good stand establishment. Hoe drills are similar to double disc press drills with better penetration characteristics. Narrow openers take less power, clear crop residues better, penetrate the soil easier and create fewer problems in covering the seed with soil than the wide openers. They however, do plug more frequently on moist clay soils.
Hoe drills give better penetration than double disc drills in firm soils.
Hoe drills can be used to seed without pre-seeding tillage because it can place the seed through more surface straw than double disc drills. Shallow seeding is difficult, especially in loose soils. The pressure setting and position adjustments on the hoes following the tractor tracks may need to be different than the other hoes to obtain the same seeding depth on all rows. Soil may build up on the press wheels in clay soils because they are usually in contact with moist soil. High speeds will cause variation in the soil coverage over the seeds.