Author(s):
Donald C. Rundquist* - CALMIT, School of Natural Resources, University Of Nebraska-Lincoln
Anatoly Gitelson - CALMIT, School of Natural Resources, University of Nebraska-Lincoln
Mark Steele - Agricultural Research and Deve;pment Center, University of Nebraska-Lincoln
Abstract:
The determination of chlorophyll and anthocyanin contents provides valuable information about the physiological status of grapevines. Perhaps more importantly, pigment configuration in leaves and berries may be related to the characteristics of the juice used in winemaking. Thus, there is a need for accurate, efficient, practical methodologies to estimate these biophysical parameters. Reflectance measurements acquired by means of properly tuned sensors may offer a mechanism for achieving that goal. The objective of this study was to develop algorithms, based on spectral reflectance, to estimate, non-destructively at leaf level, both chlorophyll (Chl) and anthocyanin (Anth) content in grapevine leaves. The developed algorithms, based on reflectance at the red edge and near-infrared for Chl and green, red-edge, and near-infrared for Anth were tested using several field-grown grape cultivars including DeChaunac, Edelweiss, Saint Croix, and Saint Pepin. Although Chl in the validation dataset was widely variable, from 3 to 506 mg m-2, the calibrated algorithm was capable of accurately predicting grape leaf Chl with RMSE < 30 mg m-2 . Similarly, Anth was also widely variable, from 3 to 45 mg m-2, yet our developed algorithms were capable of accurately predicting Anth content with RMSE <3 mg m-2. Our approach has potential for not only developing simple hand-held field instrumentation for accurate non-destructive Chl and Anth estimation but also in analyzing digital airborne or satellite imagery to assist the agricultural producer in making informed decisions regarding vineyard management.
