Increased yields with conservation tillage have been attributed to the conservation of soil water (Rao and Sustainable cropping systems are essential for agronomic, eco-Dao, 1996; Papendick and Miller, 1977) due to decreased nomic, and environmental reasons. Data from a winter wheat (Tritievaporation and cooler soil temperatures (Gauer et al., cum aestivum L.)/summer fallow rotation experiment, in eastern Oregon, was used to evaluate long-term effects of tillage, N, soil depth, 1982) and increased infiltration (Good and Smika, 1978; and precipitation on yield. The soil is a Walla Walla silt loam (coarse-Unger and McCalla, 1980; Allmaras et al., 1985; Schilsilty, mixed, mesic Typic Haploxeroll). The experiment consisted of linger, 1992; Tucker et al., 1971). Papendick and Miller three tillage treatments (moldboard plow, offset disk, and subsurface (1977) reported that wheat yield had the potential to sweep) and six N treatments. Four main time periods (1944-1951,

No abstract