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 21 ) 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.

Winter wheat yield loss in response to Avena fatua competition and effect of reduced herbicide dose rates on seed production of this species

“…Avena fatua seed production tended to be lower in competitive winter wheat stand (Site B). This is in line with findings of reduced A. fatua soil seed banks at higher wheat seeding rates implying reduced seed return [22]. It has been shown for other weeds as well that crop competition reduces weed seed production [23].…”

“…In seasons with reduced herbicide efficacy, biomass reduction of Lolium rigidum was higher in more competitive wheat cultivars compared to less competitive ones. Similarly, O'Donovan et al [22] showed that both ALS-and ACCase-inhibitors' efficacy on A. fatua increased with higher spring wheat seeding rate. Despite the very different winter wheat growth and competitiveness between our experiments, we did not find an effect of crop competitiveness on herbicide efficacy.…”

Influence of Seeding Rate, Nitrogen Management, and Micronutrient Blend Applications on Pith Expression in Solid‐Stemmed Spring Wheat

“…However, low plant populations may not always optimize grain yield. A number of studies report that higher plant populations enhance weed competitive ability and herbicide efficacy and produce higher grain yield (Beres et al, 2010b; O'Donovan et al, 2006). A study of variety selection and seeding rates ranging from 150 to 450 seeds m −2 reports that the ideal sowing density for solid‐stemmed wheat is in the range of 250 to 350 seeds m −2 (Beres et al, 2011b).…”

Managing weeds with a dualistic approach of prevention and control. A review

“…Increasing crop competitiveness with cultural tactics also improves herbicide efficacy (Derksen et al, 2002;O'Donovan et al, 2006). Scientists in the Netherlands are defining the minimum lethal herbicide dose needed for efficient weed control in various crops (Mortensen et al, 2000); lower weed density and improved crop competitiveness should enhance success of this approach also.…”