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A Comparison of Visual and Photographic Estimates of Weed Biomass and Weed Control1

Published online by Cambridge University Press:  20 January 2017

Christophe Neeser ,
Alex R. Martin ,
Peter Juroszek  and
David A. Mortensen
Christophe Neeser
Affiliation:
Department of Agronomy, University of Nebraska, Lincoln, NE 68583-0915
Alex R. Martin
Affiliation:
Department of Agronomy, University of Nebraska, Lincoln, NE 68583-0915
Peter Juroszek
Affiliation:
Institut für Pflanzenbau University of Bonn, 53115 Bonn, Germany
David A. Mortensen*
Affiliation:
Department of Agronomy, University of Nebraska, Lincoln, NE 68583-0915
*
Corresponding author's E-mail: dmortensen1@unl.edu.
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Abstract

The objective of this study was to compare the consistency and accuracy of visually estimated weed biomass and weed control data to data obtained through image analysis. Weed biomass and weed control were evaluated in soybean herbicide efficacy trials conducted at the University of Nebraska–Lincoln during 1992 and 1993. Measurements were based on visual estimates and on aerial photographs taken at a height of 3.5 m above the soil surface. Photographs were digitized and classified, producing pixel values for broadleaf weeds, grass weeds, soybean, and soil. Percent weed cover was calculated in relation to the crop canopy, based on the respective number of pixels per image. Visual and photographic ratings of weed biomass and of weed control were not closely correlated. In the first year the visual method discriminated between more treatments than the photographic method, but the opposite occurred in the second year. The photographic method predicted yield more closely than the visual estimates. We concluded that visual estimates were less consistent and more subject to observer bias than measurements obtained with the photographic method.

Keywords

SoybeanGlycine max (L.) MerrImage analysiscanopyPOST, postemergencePPI, preplant incorporatedPRE, preemergence
Type
Research Article
Information
Weed Technology , Volume 14 , Issue 3 , September 2000 , pp. 586 - 590
Copyright
Copyright © Weed Science Society of America 

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