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This article in AJ

  1. Vol. 68 No. 6, p. 843-848
     
    Received: Apr 23, 1975


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doi:10.2134/agronj1976.00021962006800060002x

Reflectant Induced Modification of Soybean Canopy Radiation Balance IV. Leaf and Canopy Temperature1

  1. Maximo W. Baradas,
  2. Blaine L. Blad and
  3. Norman J. Rosenberg2

Abstract

Abstract

Potential water-savings and increased water use efficiency may result from reflectant-induced modification of the canopy radiation balance. This report is the fourth in a series of papers describing reflectant treatment effects on the radiation balance. The purpose of this study was to determine the effect of reflectant treatment on the leaf and canopy temperature of two soybean [Glycine max (L.) Merr] cultivars which display contrasting types of canopy architecture. ‘Amsoy’ and ‘Beeson’ which have erectophile and planophile canopies, respectively, were used. Leaf temperature was measured with leaf thermocouples and canopy temperature with an infrared thermometer.

Near solar noon, the reflectorized Amsoy canopy was 1 to 2 C warmer than the untreated canopy. Smaller but qualitatively similar differences were observed in the Beeson cultivar. Whether reflectorized or not, the Amsoy canopies were warmer than the corresponding Beeson canopies. The increased temperature of the treated plants was corroborated by thermal imagery from an airborne scanner.

The unexpected temperature increase of the reflectorized crop was due to two major factors. The first, and probably most important, was a decrease in the longwave emissivity of the treated crop. This, in turn, caused reduced cooling rates and also caused the absorptivity to emissivity ratio (α/ε) to be increased. The second factor was reduced transpiration rates which were observed for the reflectorized crop.

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