Wild oat reduced light penetration and growth of dwarf hard red spring wheat in field experiments performed under nonlimiting nitrogen and moisture conditions. Wild oat grew taller than wheat and had a greater portion of its canopy above 60 cm at maturity. Light penetration in a mixed canopy was similar to that in a monoculture wheat canopy when wild oat was clipped to the height of the wheat. A mathematical model was developed which accurately predicted the reduction in the growth rate of wheat from wild oat interference. The model also predicted that interference from wild oat was due to reduced leaf area of wheat at early growth stages and low wild oat densities, and reduced light penetration to wheat leaves at later growth stages and higher densities of wild oat.
