Author:
O’SULLIVAN P. A.,KOSSATZ V. C.,WEISS G. M.,DEW D. A.
Abstract
Experiments were conducted to determine if a relationship exists between yield loss of barley and various indicators of Canada thistle density. Correlation coefficients between barley yields and total numbers of Canada thistle shoots/m2, numbers of shoots/m2 taller than 0.5 m, numbers of flowering shoots/m2 or shoot dry weight (g/m2), using two representations of the density data (untransformed or square root transformation) were significant at P < 0.01. The data for percent yield loss of barley and total numbers of Canada thistle shoots/m2 were analyzed by regression using both representations of the data and yielded the following equations:[Formula: see text]and[Formula: see text]where ŷ = estimated percent yield loss of barley, x = the total number of Canada thistle shoots/m2 and 0.85 and 7.6 were the indices of competition for Eqs. 1 and 2, respectively. Equation 2 probably provides a more accurate estimate of barley yield loss at low levels of Canada thistle infestation [Formula: see text] whereas either equation is acceptable at intermediate-to-high levels of infestation (5–45 shoots/m2). The 95% confidence limits for Eqs. 1 and 2 and for the estimated percent barley yield losses when four different sample sizes (n = 1, 5, 10 or 20) are used to estimate the thistle density mean are presented. The Eq. 2 index of competition is extrapolated to other crops. Comparing a Canada thistle shoot with a wild oat plant in barley, Canada thistle may be about 3.4 times as competitive as wild oats.
Publisher
Canadian Science Publishing
Subject
Horticulture,Plant Science,Agronomy and Crop Science
Cited by
50 articles.
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