An Index of Competition for Estimating Loss of Rape Due to Wild Oats

Dew, D. A.; Keys, C. H.

doi:10.4141/cjps76-170

Cited by 39 publications

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“…Considerable research has been conducted to document the effects of wild oat on crop yield in conventional tillage systems (Dew 1972;Dew and Keys 1976). Yield losses in cereal and oilseed crops can be considerable, especially when wild oat emerges ahead of the crop (O'Donovan et al 1985).…”

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Effect of barley plant density on wild oat interference, shoot biomass and seed yield under zero tillage

O’Donovan¹,

Newman²,

Harker³

et al. 1999

Can. J. Plant Sci.

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. 1999. Effect of barley plant density on wild oat interference, shoot biomass and seed yield under zero tillage. Can. J. Soil Sci. 79: 655-662. There has been little research aimed at developing regression models to describe the effects of barley and wild oat plant density on barley yield loss, or wild oat biomass and seed yield. Such models are an important component of integrated weed management systems, and can help determine when weed control with herbicides is economical. Field experiments were conducted over 4 yr at Vegreville, Alberta, to determine the interactive effects of wild oat and barley plant density on barley and wild oat variables in a zero tillage system. A nonlinear regression model in most cases provided good descriptions of barley yield loss, wild oat shoot dry weight, and wild oat seed yield as functions of wild oat and barley plant densities. The interactive effect of wild oat and barley plant density on percentage barley yield loss did not differ significantly (P = 0.05) among years. A pooled regression model describing barley yield loss accounted for 57% of the variation, and provides a means of estimating yield loss due to wild oat in barley grown under zero tillage. Barley yield loss increased as wild oat density increased but the magnitude of the yield loss diminished with increasing barley plant density. Wild oat economic threshold densities varied among years, and were strongly influenced by barley price and expected wild oatfree yield. Economic thresholds were greater at higher barley plant densities. Barley seed weight decreased with increasing barley plant density, and to a lesser extent with increasing wild oat density. The interactive effect of wild oat and barley plant density on wild oat seed yield varied significantly with year, and appeared to be influenced by climatic conditions. The cooler, wetter spring of 1996 favored wild oat seed production (by several orders of magnitude) compared with the relatively warmer and drier spring of 1995. Each year wild oat seed yield and shoot dry weight decreased as barley plant density increased. The results suggest that seeding barley at relatively high rates may reduce the need for wild oat control with herbicides in zero tillage systems.Key words: Zero tillage, wild oat interference, barley seeding rate, nonlinear regression O'Donovan, J. T., Newman, J. C., Harker, K. N., Blackshaw, R. E. et McAndrew, D. W. 1999. Effet de la densité de peuplement de l'orge sur l'importance de la concurrence exercée par la folle avoine, ainsi que sur la production végétative et semencière de la mauvaise herbe en régime de semis direct. Can. J. Plant Sci. 79: 655-662. Il n'y a eu jusqu'ici que peu de tentatives de modélisation par régression pour décrire les effets de la densité de peuplement de l'orge et de la folle avoine sur le manque à produire de l'orge ou sur le rendement en biomasse et en graines de la folle avoine. Ce type de modèle constitue pourtant une importante composante des systèmes de lutte intégrée contre les mauvaises herbes et il pe...

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confidence: 99%

Effect of barley plant density on wild oat interference, shoot biomass and seed yield under zero tillage

O’Donovan¹,

Newman²,

Harker³

et al. 1999

Can. J. Plant Sci.

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“…Mots cl6s: Pr6cocit6 relative de lev6e, densitd de peupiement, repousses d'orge, canola, hyperbole rectangulai re Weed density has been the variable most often used to describe the effects of weeds on canola yield (Dew and Keys 1976; O'Sullivan er al. 1985).…”

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Seed yields of canola and volunteer barley as influenced by their relative times of emergence

O’Donovan¹

1992

Can. J. Plant Sci.

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“…) has been shown to be a highly competitive weed to barley (Hordeum vulgare L.) (O'-Sullivan et al 1982) and wheat (Triticum aestivum L.) (Hodgson 1968). The weed is widespread in western Canada (Thomas 1980), and is the most serious perennial weed problem (Friesen 1968 Dew (1972) and Dew and Keys (1976) Dew (1972) and Dew and Keys ( 1976) may occur between these crops and other weeds such as Canada thistle.…”

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Indices of Competition for Estimating Rapeseed Yield Loss Due to Canada Thistle

O’Sullivan¹,

Weiss²,

Kossatz³

1985

Can. J. Plant Sci.

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Data were collected from nine farm fields over 2 yr to determine the relationship between percent yield loss of rapeseed and density of Canada thistle. Regression analyses of the data for percent yield loss of rapeseed and numbers of thistle shoots per square metre, using two representations of the data (untransformed and square root transformation), yielded the following equations:[Formula: see text]and[Formula: see text]where ŷ = estimated percent yield loss of rapeseed, x = the number of Canada thistle shoots per square metre, and 1.48 and 10.42 are the indices of competition for Eqs. 1 and 2, respectively. Equation 1 provides a more accurate estimate of percent yield loss at all levels of thistle infestation. Equation 2 provides acceptable estimates of yield loss at intermediate levels of infestation (5–40 shoots/m2) and is presented for comparitive purposes since the index of competition (10.42) is near the value proposed as a result of extrapolation from earlier studies (10.6) which utilized square root transformation of the data. The significance of this is discussed. The 95% confidence limits for Eq. 1 for the estimated percent rapeseed yield loss when four different samples sizes (n = 1, 5, 10 and 20) are used to estimate the number of thistle shoots per square metre are presented. An example of the utility of the linear equation is presented.Key words: Rapeseed, Canada thistle, crop loss, competition

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An Index of Competition for Estimating Loss of Rape Due to Wild Oats

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Cited by 39 publications

References 0 publications

Effect of barley plant density on wild oat interference, shoot biomass and seed yield under zero tillage

Effect of barley plant density on wild oat interference, shoot biomass and seed yield under zero tillage

Seed yields of canola and volunteer barley as influenced by their relative times of emergence

Indices of Competition for Estimating Rapeseed Yield Loss Due to Canada Thistle

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