Effects of fertilizer and stubble burning on downy brome competition in winter wheat

Increased downy brome (Bromus tectorum) infestation is one of the dominant impediments to adoption of conservation tillage. Surface residues often increase grassy weed competition and lower the yield of cereal crops. Crop residue and fertilizer placement effects on downy brome growth and nutrient uptake in relation to that of winter wheat (Triticum aestivum L.) were conducted in two separate years; one involving conventional (plow) tillage and the other no‐till. Crop residue (burning versus no burning) and fertilizer placement (broadcasting versus subsurface banding) differentials were present both years. The conventional‐till study also included nitrogen (N) rates from 0 to 168 kg/ha and an N only versus nitrogen+phosphorus+sulfur (N+P+S) comparison. Burning increased early‐spring wheat growth substantially, with only limited effect on downy brome population or growth. Broadcasting of fertilizer increased downy brome density and growth compared to banding. Wheat, in contrast, had greater growth and higher N uptake from banded fertilizer. Increasing N increased both seedling survival and culm production of downy brome. Addition of N+P+S increased both wheat and downy brome growth more than N applied alone, but wheat appeared more responsive. Wheat yield tended to be less with higher downy brome infestation.