Authors: Nansen, Christian¹; Sidumo, Amelia Jorge²; Capareda, Sergio³

Source: Applied Spectroscopy, Volume 64, Issue 6, Pages 158A-174A and 563-689 (June 2010) , pp. 627-636(10)

Publisher: Society for Applied Spectroscopy

Abstract:

A considerable challenge in applied agricultural use of reflection-based spectroscopy is that most analytical approaches are quite sensitive to radiometric noise and/or low radiometric repeatability. In this study, hyperspectral imaging data were acquired from individual maize leaves and the main objective was to evaluate a classification system for detection of drought stress levels and spider mite infestation levels across maize hybrids and vertical position of maize leaves. A second objective was to estimate biomass and biofuel potential (heating value) of growing maize plants. Stepwise discriminant analysis was used to identify the five spectral bands (440, 462, 652, 706, and 784 nm) that contributed most to the classification of three levels of drought stress (moderate, subtle, and none) across hybrids, leaf position, and spider mite infestation. Regarding the five selected spectral bands, average reflectance values and standard variogram parameters ("nugget", "sill", and "range" derived from variogram analysis) were examined as indicators of spider mite and/or drought stress. There was consistent significant effect of drought stress on average reflectance values, while only one spectral band responded significantly to spider mite infestations. Different variogram parameters provided reliable indications of spider mite infestation and drought stress. Based on independent validation, variogram parameters could be used to accurately predict spider mite density but were less effective as indicators of drought stress. In addition, variogram parameters were used as explanatory variables to predict biomass and biofuel potential of individual maize plants. The potential of using variogram analysis as part of hyperspectral imaging analysis is discussed.

Keywords: MAIZE; HYPERSPECTRAL DATA; VARIOGRAM ANALYSIS; DROUGHT STRESS; SPIDER MITES; SILAGE; BIOFUEL; AGRICULTURE

Document Type: Research article

DOI: http://dx.doi.org/10.1366/000370210791414272

Affiliations: 1: Texas AgriLife Research, 1102 East FM 1294, Lubbock, Texas 79403; Department of Plant and Soil Science, Texas Tech University, Campus Box 42122, Lubbock, Texas, 79409 2: Department of Plant and Soil Science, Texas Tech University, Campus Box 42122, Lubbock, Texas, 79409 3: Biological and Agronomical Engineering, Texas A&M University, College Station, Texas 77843

Publication date: 2010-06-01

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