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Accueil du site → Projets de développement → Projets de recherche pour le Développement → 2009 → EVALUATION OF TRIANGULAR SPECTRAL INDICES FOR PREDICTING MID-SEASON NITROGEN LEVELS IN DRYLAND WHEAT

United States Department of Agriculture (USDA) 2009

EVALUATION OF TRIANGULAR SPECTRAL INDICES FOR PREDICTING MID-SEASON NITROGEN LEVELS IN DRYLAND WHEAT

Nitrogen Dryland Wheat

United States Department of Agriculture (USDA) Research, Education & Economics Information System (REEIS)

Titre : EVALUATION OF TRIANGULAR SPECTRAL INDICES FOR PREDICTING MID-SEASON NITROGEN LEVELS IN DRYLAND WHEAT

Identification : 5356-21610-001-03

Pays : Etats Unis

Durée : Apr 01, 2009 à Mar 31, 2011

Objectif
To : (1) test triangular spectral indices for predicting leaf chlorophyll content of dryland wheat at late season, (2) assess the spectral index-chlorophyll relationships with multispectral satellite and aircraft imagery, and (3) investigate variation in the indices with growth and development of spring wheat.

Descriptif
For objectives 1 and 2, an existing three-year (2001-04) database consists of SPAD chlorophyll, leaf nitrogen, LAI, and spectral canopy reflectance from wheat fields in Montana. Ikonos and Quickbird satellite imagery are available in the blue, green, red, and NIR wavebands, and DuncanTech aircraft imagery in the green, red, and NIR bands. The software ENVI will be used for extracting image reflectance values for ground sampling points and computing the triangular vegetation index (TVI), triangular greenness index (TGI), and other indices. All ground reference variables will be correlated with image reflectance data as needed to derive linear regression models predicting crop N attributes at mid-season. Spectral indices will be correlated with under a broad range of biomass, leaf area index, and crop cover conditions. Linear prediction models will be validated using a set of measurements of chlorophyll and N content assigned for this purpose. For objective 3, crop canopy reflectance will be measured in small plots using photodiode sensors giving sensitivity in the blue, green, red, and near infrared wavebands. The downward facing sensors will be permanently mounted 1-m above the crop canopy. To obtain reflectance, measurements will be referenced against incoming radiation as measured with a skyward facing sensor. Crop canopy reflectance will be continuously measured and recorded over the growing season in 10-s increments by means of an automated data logger. Flag leaves will be subsampled from each plot. Chlorophyll measurements will be obtained for each leaf using a SPAD chlorophyll meter. Nadir and oblique views will be recorded of each plot using a 10 megapixel digital camera to produce ultra large-scale images. Spectrophotometry will be used for laboratory determination of chlorophyll concentration in 80% aqueous acetone. Spectral reflectance will be measured from each leaf using an ASD radiometer and leaf clip. The resulting data set will be used to validate performance of triangular spectral indices as predicted by the Prospect-SAIL radiative transfer model.

Présentation : USDA

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