SOYBEAN CULTIVAR RESPONSE TO TILLAGE SYSTEMS

Modern crop cultivars were developed in cleanly tilled environments. As reduced- and no-till production increases, we must study cultivar responses to these planting conditions to assist growers with cultivar selection for specific tillage situations. In addition, if certain cultivars respond better to a tillage system, this genetic variability could be useful in breeding programs. A field study was conducted to compare six soybean [Glycine max (L.) Merr.] cultivars of different maturities and growth habits in three tillage systems. A Hastings silt loam soil (fine, montmorillonitic, mesic Udic Argiustoll) was used in 1982 and 1983, and a Crete silt loam soil (fine, montmorrilonitic, mesic Pachic Argiustoll) was used in 1984. Tillage treatments were double disk, single disk, and no-till. Soil profiles were at field capacity at planting in all years. Tillage did not affect yield, and cultivars responded similarly to tillage systems; the best yielding cultivars in tilled systems were also best yielding in the no-till system. There is no immediate need for cultivar performance testing in different tillage systems. However, in one year ''Mead'' yielded 15% more in no-till than in tilled systems, whereas ''Williams 82'' yielded 8% less in no-till than in tilled systems. This response may be related to a slight plant density difference between the two cultivars or genotypic differences. Effects of residue cover on evaporation are of less consequence when soils are at field capacity at planting. Thus, cultivar and tillage responses may be different than those reported here when soil moisture is deficient at planting.