Wheat Seeding Rate Influences Herbicide Performance in Wild Oat (Avena fatua L.)

Abstract

Field experiments were conducted at three locations in Alberta for 3 yr to determine if spring wheat (Triticum aestivum L.) seeding rate (75 and 150 kg ha−1) influenced the effects of recommended and reduced herbicide rates on wild oat (Avena fatua L.) shoot biomass, wild oat seed in the soil seed bank, and wheat yield and net economic return. Wild oat biomass and seed in the soil seed bank decreased nonlinearly at both seeding rates as herbicide rates increased. The herbicides were more effective in reducing wild oat shoot biomass and seed in the soil seed bank when wheat was seeded at the higher rate. The lowest wheat yields and net economic returns occurred when no herbicides were applied and both variables increased nonlinearly with increasing herbicide rate. In most cases, wheat yield and net economic return were greater at the higher seeding rate. On average, wheat yield improved by 19% and net economic return by 16% when wheat was seeded at the higher rate. The results indicate that seeding wheat at relatively high rates can contribute positively to herbicide performance and result in better wild oat management and higher wheat yields and economic returns. In some cases, there was little difference between applying the herbicides at 75 or 100% of the recommended rate but reducing rates below 75% almost always resulted in higher wild oat shoot biomass and seed, and reduced yields and net economic returns, even at the higher wheat seeding rate.