Field studies were conducted for two years at two locations near Pendleton and Moro, OR to evaluate the influence of single sub-surface nitrogen (N) fertilizer application timings and multiple N applications on downy brome and winter wheat growth and yield. N applications in fallow, at planting, during the crop season, and several split N application timings were compared to evaluate downy brome interference in winter wheat. N application rates varied between locations as a function of average annual precipitation and accepted agricultural practice. Pendleton and Moro were considered high and low precipitation sites, respectively. At Pendleton in a year of above average precipitation, N applied at planting, in-crop, or split applications of N with part of N applied at planting and part in-crop, increased downy brome dry matter production compared to N applied in fallow. Downy brome infestation eliminated otherwise positive wheat yield benefits of split N application compared to the conventional commercial practice of N application in fallow. In a year of moderate precipitation, N applications at planting, in-crop, or split N applications did not benefit wheat yield compared to N application in fallow, but downy brome dry matter was increased. In a dry season, N rates and timings did not increase downy brome dry weight or wheat grain yield. In the absence of downy brome, alternative N application techniques increased wheat yield only under high growing season precipitation.