Influence of wild oat (Avena fatua) relative time of emergence and density on cultivated oat yield, wild oat seed production, and wild oat contamination

Abstract

Wild oat is a serious weed in cultivated oat because there are no herbicides to selectively control it. Considering the effect of time of emergence on weed–crop interference is critical for the development of accurate crop yield loss models and weed density thresholds. Therefore, field experiments were conducted at two locations in Saskatchewan, Canada, in 2002 and 2003 to determine the effect of wild oat density and time of emergence on cultivated oat yield and quality. Wild oat was planted at 50 growing degree day (GDD) intervals ranging from 100 GDD before to 100 GDD after crop planting. Wild oat density ranged from 0 to 320 plants m−2. High densities of early emerging wild oat greatly reduced cultivated oat yield and increased wild oat contamination, with observed oat yield losses as great as 70% and wild oat contamination levels of 15%. Wild oat that emerged before cultivated oat caused considerably more yield and quality loss and had higher reproductive output than wild oat that emerged after cultivated oat. The yield loss caused by individual wild oat plants at low densities (parameter I) ranged from 0.40 to 0.49%. The effect of relative time of wild oat emergence (parameter C) always varied significantly between site-years. However, little variation in absolute values within site-years was observed for cultivated oat yield loss, wild oat seed production, and wild oat contamination, suggesting that relative time of wild oat emergence influences all similarly. The results of this study emphasize both the need to control early emerging wild oat, as well as the importance of time of emergence in the prediction of crop yield loss. Furthermore, our approach of conducting an emergence study based on thermal time is novel and demonstrates a robust, mechanistic method of estimating crop yield losses due to relative time of emergence.

Management of wild oat (Avena fatua L.) in tame oat (Avena sativa L.) with early seeding dates and high seeding rates

“…Grain yield was maximized at 350 seeds m (2 at both high and low wild oat densities, which indicates that higher seeding rates can be used to control higher densities of wild oat. This result corroborates the work of Wildeman (2004) and Willenborg et al (2005a). Earlier research under conditions relatively free of wild oat found that seeding rate did not have a significant effect on grain yield (Mohr et al 2000).…”

“…This conclusion is also supported by Willenborg et al (2005a) and Wildeman (2004). The individual yield components showed no response to wild oat density but an effect for seeds m (2 was observed, indicating the difficulty in detecting wild oat density effects on the yield components of tame oat.…”

“…At Indian Head, in 2003, the wild oat density was 8, 2, 3, and 0 plants m (2 for early May, mid May, early June and mid June, respectively. This response of wild oat emergence and density to environmental conditions was also observed by Willenborg (2005a). Wild oat panicle density and wild oat biomass were affected by a site ) wild oat )seeding date interaction.…”

Effects of relative time of emergence and density of wild oat (Avena fatua L.) on oat quality

“…Averaged over wild oat density and time of emergence treatments, thin kernel percentages were greater and plump kernel percentages lower at Indian Head in 2003 than 2002 (Table 3). These differences were likely a consequence of reduced moisture levels and substantial competition from wild oat during grain filling (Willenborg et al 2005). Limited moisture availability frequently results in reduced seed set and filling caused by reductions in leaf area, photosynthesis, and assimilate transfer (Passioura 1994).…”

Influence of wild oat plant density on spring wheat yield

“…Moreover, uneven germination makes control of wild oat difficult, because new plants are likely to emerge after control measures were applied. Willenborg et al (2005) in a study of the influence of time of emergence of wild oat on yield of common oat showed that early emerging wild oat causes more yield loss than late-emerging. Predicted yield losses caused by 100 wild oat plants m -2 in one of the experimental sites were 45% and 20%, depending on the relative time of emergence of the wild oat, but the estimated slope parameter (I) was 0.4, which is much lower than in the models in this study (Table 5), indicating lower competitive ability of oat comparing to spring wheat.…”