HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Viña, A. Articles by Schepers, J. Search for Related Content PubMed Articles by Viña, A. Articles by Schepers, J. Agricola Articles by Viña, A. Articles by Schepers, J. Related Collections Maize Remote Sensing

Monitoring Maize (Zea mays L.) Phenology with Remote Sensing

^a Cent. for Advanced Land Manage. Information Technol., and School of Nat. Resour., Univ. of Nebraska–Lincoln, 113 Nebraska Hall, Lincoln, NE 68588-0517
^b Cent. for Advanced Land Manage. Information Technol., Univ. of Nebraska–Lincoln, 113 Nebraska Hall, Lincoln, NE 68588-0517
^c USDA-ARS and Dep. of Agron. and Hortic., 113 Keim Hall, Univ. of Nebraska–Lincoln, Lincoln, NE 68583-0915

View larger version (29K): [in a new window]   Fig. 1. (A) Temporal profiles of green vegetation fraction of the fields studied, during the 2001 and 2002 growing seasons. (B) Temporal progression of total chlorophyll content in top-collar maize leaves during the growing season of 2002. Error bars correspond to one standard deviation. Accumulated growing degree days (AGDD) were calculated starting from 1 May. Inset: Relation between total chlorophyll content in mg/m2 and chlorophyll index of 70 maize leaves {Chl = 723.04 x [(NIR/Red Edge) – 1] – 10.76; r2 = 0.93; p < 0.001}. The coefficients obtained from this equation were used to calculate leaf chlorophyll content of top-collar leaves along the growing season of 2002.

View larger version (14K): [in a new window]   Fig. 2. Normalized difference vegetation index (NDVI) and visible atmospherically resistant indices (VARIGreen and VARIRed Edge) vs. green vegetation fraction of maize during the 2002 growing season, before silking. Normalized difference vegetation index showed a nonlinear relationship with green vegetation fraction while VARI showed linear relationships, with VARIGreen having a higher dynamic range to allocate green vegetation fraction values than VARIRed Edge.

View larger version (31K): [in a new window]   Fig. 3. Temporal profiles of vegetation indices [normalized difference vegetation index (NDVI) and visible atmospherically resistant indices (VARIGreen and VARIRed Edge)] obtained in irrigated (left panel) and dryland (right panel) fields during the 2001 and 2002 growing seasons. Accumulated growing degree days (AGDD) were calculated starting from 1 May.

View larger version (32K): [in a new window]   Fig. 4. (A) Spectral reflectance of maize tassels. Error bars correspond to one standard deviation. A typical reflectance spectrum of a healthy maize leaf is also shown for comparison. (B) Effect of the presence of maize tassels in reciprocal reflectance spectra of canopy. Spectral readings were obtained in the same spot before and after removing all the tassels within the field of view of the spectroradiometer. The dotted line represents the probability of a two-sample t test, performed at each wavelength (n = 10), to test whether there is a significant difference among reciprocal reflectance spectra of a canopy with tassels and that with the tassels removed. These analyses where performed after checking for variance homogeneity.

View larger version (21K): [in a new window]   Fig. 5. Scaled first derivative (SFD; Eq. [6]) of normalized difference vegetation index (NDVI) and visible atmospherically resistant index (VARIGreen) with respect to accumulated growing degree days. Arrows show the dates of critical phenological transitions.