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Agronomy Journal Abstract -

Use of Spectral Vegetation Indices to Infer Leaf Area, Evapotranspiration and Yield: II. Results


This article in AJ

  1. Vol. 82 No. 3, p. 630-636
    Received: Dec 22, 1986

    * Corresponding author(s):
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  1. C. L. Wiegand  and
  2. A. J. Richardson
  1. USDA-ARS, Remote Sens. Res. Unit, 2413 E. Bus. Hwy. 83, Weslaco, TX 78596



Better methods of interpreting spectral observations of crop canopies in terms of agronomic characteristics such as green leaf area index (L) and aboveground dry phytomass (DM), and for estimating economic yield (Y) are needed. The equations proposed were applied to single year experiments with Triticum aestivum L. and Triticum durum Desf., Gossypium hirsutum L., and Zea mays L. in order to illustrate and further test them. As predicted, fractional photosynthetically active radiation absorption (FPAR) could be estimated from vegetation indices (VI) such as perpendicular vegetation index (PVI) and the normalized difference (ND) about as well as from L. Generally, L/VI and FPAR/L-verbalized as L as a function of VI, and FPAR as a function of L-were exponential relations whereas FPAR/VI were linear or nearly linear functions. The DM, Y, and the harvest index (Y/DM) were linearly related to PVI averaged for several dates during late vegetative development for wheat and corn, indicating that relative yields for both crops had been set by that development stage. The functional relations L/VI, FPAR/L, FPAR/VI, Y/VI, DM/VI, ∑APAR/∑VI, DM/∑APAR, Y/∑VI and (Y/DM)/VI where APAR is daily absorbed PAR (MJ m−2 d−1) presented document that direct spectral observations and the equations incorporating them do provide additional analytical tools for interpreting crop development, growth, and yield.

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