A Digital Photographic Technique for Assessing Forage Utilization

Changes in forage utilization have been difficult to measure non-destructively without some level of subjectivity. This subjectivity, combined with a lack of reproducibility of visual estimates, has made forage utilization measurement techniques a topic of considerable discussion. The objective of t...

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Bibliographic Details
Published in:Journal of range management 2003-03, Vol.56 (2), p.140-145
Main Authors: Hyder, P. W., E. L. Fredrickson, M. D. Remmenga, R. E. Estell, R. D. Pieper, Anderson, D. M.
Format: Article
Language:English
Subjects:
Alfalfa
Defoliation
Digital photography
Estimate reliability
Estimation methods
Forage
Image analysis
Linear regression
Measurement/Sampling
Plants
Range management
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Summary:Changes in forage utilization have been difficult to measure non-destructively without some level of subjectivity. This subjectivity, combined with a lack of reproducibility of visual estimates, has made forage utilization measurement techniques a topic of considerable discussion. The objective of this study was to develop and test the accuracy and repeatability of an objective, computer-based technique for measuring changes in plant biomass. Digital photographs of target plants acquired before and after partial defoliation were analyzed using readily available image analysis software. Resulting data were used to develop a simple linear random coefficient model (RC) for estimation of plant biomass removed based on the area of the plant in the photo. Sample collection took approximately 20 minutes/plant for alfalfa (Medicago sativa L.). Analysis of images took another 60 to 90 minutes. Regression analysis gave an R2of 0.969 for predicted vs. observed plant weights. Testing this model using 10 alfalfa plants yielded weight estimates of defoliated plants accurate to within +/- 8.5%. The advantage of the RC model is its ability to use easily obtained coefficients from simple linear regression models developed from each plant in a way that accounts for the lack of independence between samples within an individual plant. The technique described here offers an objective and accurate method for measuring changes in plant biomass with possible applications in ecology, botany, and range science. In particular, application of this technique for estimating forage utilization may improve accuracy of estimates and, thereby, improve range management practices. /// Los cambios en la utilización de forraje han sido difíciles de medir en forma no destructiva sin un grado de subjetividad. Esta subjetividad, combinada con la carencia reproducción de las estimaciones visuales, ha hecho que las técnicas de medición de utilización de forraje sea un tópico de considerable discusión. El objetivo de este estudio fue desarrollar y probar la certeza y repetibilidad de una técnica computacional objetiva para medir la biomasa vegetal. Fotografías digitales de plantas de interés tomadas antes y después de ser sujetas a una defoliación parcial fueron analizadas utilizando programas de computación ya disponibles para el análisis de imágenes. Los datos resultantes fueron utilizados para desarrollar un modelo lineal simple de coeficiente aleatorio (RC) para estimar la biomasa vegetal removi
ISSN:0022-409X
2162-2728
DOI:10.2307/4003897