Information on response of soybean [Glycine max (L.) Merr.] cultivars to reduced tillage systems in northern dryland areas is limited. A 4-yr field study (1984 to 1987) was conducted to evaluate the effect of tillage system, weed control method, and cultivar maturity on soybean seed yield variables. An early and a late-maturing soybean cultivar were grown on a Fargo clay (fine, montmorillonitic frigid Vertic Haplaquoll) on established tillage plots. Tillage systems included conventional (moldboard plow) and three reduced tillage systems (sweep, intertill, and no-till) with herbicides or herbicides plus cultivation for weed control. Climatic conditions resulted in differences among years in seed yield, seed weight, seed moisture, seed oil concentration, and seed oil yield. These seed variables were not significantly influenced by tillage system, weed control method, or cultivar maturity when grown in rotation with barley (Hordeum vulgare L.), but showed significant interactions. Cultivation for weed control depressed seed yield and weight of only the early cultivar. Early plant water stress (June and July) lowered yield of the early cultivar more than the late cultivar. Early cultivar no-till yields (1240 kg ha?1) were greater than tilled system yields (average 1070 kg ha?1). while late cultivar yields were similar among systems (average 1420 kg ha?1). An early maturing cultivar performed similarly to a late-maturing cultivar irrespective of tillage system unless early plant water stress was encountered. Fall application of granular herbicide provided good weed control, but cultivation for weed control was not beneficial for the yields parameters measured.
