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The use of Biologically Realistic Equations to Describe the Effects of Weed Density and Relative Time of Emergence on Crop Yield

Published online by Cambridge University Press:  12 June 2017

Roger Cousens ,
Philip Brain ,
John T. O'Donovan  and
P. Ashley O'Sullivan
Roger Cousens
Affiliation:
Weed Sci. and Biometrician, Dep. Agric. Sci., Bristol Univ., Long Ashton Res. Stn., Bristol, England BS18 9AF
Philip Brain
Affiliation:
Weed Sci. and Biometrician, Dep. Agric. Sci., Bristol Univ., Long Ashton Res. Stn., Bristol, England BS18 9AF
John T. O'Donovan
Affiliation:
Weed Sci., Alberta Env. Centre, Vegreville, Alberta TOB 4LO
P. Ashley O'Sullivan
Affiliation:
Weed Sci., Agric. Can. Res. Stn. Lacombe, Alberta TOC ISO
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Abstract

A model, based on a rectangular hyperbola, has been developed to describe the relationship between population density and relative time of seedling emergence of wild oat (Avena fatua L. # AVEFA) and yield of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.). The equation is where yL is percent yield loss, D is weed density, T is relative time of emergence of weed and crop, and a, b, and c are nonlinear regression coefficients. Significant differences in fitted equations were found between years. From the values of regression coefficients it was concluded that barley is a better competitor than wheat and is less affected by late-emerging wild oat. The model was tested on previously published data. It provided only a slightly better description of the data than a multiple-regression model, but avoided a number of undesirable, implausible properties inherent in the more frequently used approach. In particular, the model does not predict a loss in yield when no weeds are present or a yield increase from late-emerging weeds.

Keywords

Nonlinear modelscompetitionAvena fatuaAVEFA
Type
Special Topics
Information
Weed Science , Volume 35 , Issue 5 , September 1987 , pp. 720 - 725
Copyright
Copyright © 1987 by the Weed Science Society of America 

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References

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