Field experiments were conducted at the Caddo Research Station near Ft. Cobb, OK and at the Agronomy Research Station near Perkins, OK to measure the effects of seven crownbeard (Verbesina encelioides) densities on peanut (Arachis hypogaea) yield. The seven densities evaluated were 0 (the weed-free check), 0.2, 0.4, 0.8, 1.6, 2.4, and 3.2 weeds/m of row. Data collected consisted of dry weed biomass and peanut yields. Correlation between weed density and dry weed biomass, dry weed biomass and peanut yield (kg/ha), dry weed biomass and peanut yield loss (percentage of check), weed density and peanut yield (kg/ha), and weed density and peanut yield loss (percentage of check) were evaluated. For each weed/m of row, dry weed biomass increased by 0.34 kg/m row. Dry weed biomass was a good predictor of peanut yield. For each kilogram of dry weed biomass/ m row, a 1900-kg/ha or 46.3% reduction in peanut yield occurred. Weed density was also a good predictor of peanut yield. A 559-kg/ha reduction or 16% increase in peanut yield loss occurred for each weed/m row. Peanut yield was reduced approximately 50% when crownbeard density increased to 3.2 weeds/m row.
Nomenclature: Crownbeard, Verbesina encelioides (Cav.) Benth. & Hook. f. ex Gray #3 VEEEN; peanut, Arachis hypogaea L.
Additional index words: Competition, dry weed biomass.