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This article in AJ

  1. Vol. 64 No. 3, p. 368-373
     
    Received: Oct 8, 1971
    Published: May, 1972


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doi:10.2134/agronj1972.00021962006400030034x

Soil Surface Water Depletion and Leaf Temperature1

  1. A. R. Aston and
  2. C. H. M. van Bavel2

Abstract

Abstract

This work explores the feasibility of the remote detection of water depletion in a cropped field. It proposes that this may be accomplished by detecting the increase in the visible and thermal radiant heat loads upon plant leaves when the underlying soil surface dries. A theoretical model was constructed, relating leaf temperature to soil surface temperature.

Parallel experiments were done using a grey podzolic soil. It was found that in spite of an increase of 15% in reflectivity upon drying, there was an increase in soil surface temperature from 20 to 50 C. The increased shortwave and longwave radiant loads on leaf arrays in the experiments, resulted in leaf temperature increases of 2.5, .5, and 2 C in dry blotting paper, wet blotting paper, and leaves of the southern pea (Vigna sinensis), respectively.

The leaf energy balance-soil water depletion model predicted these increases, as well as the absolute temperatures, with an accuracy of 1 and 5% for the artificial and real leaves, respectively.

The findings of this study affirm that a technology can be developed for the remote detection of soil water depletion in field crops, but that the temperature differences involved are both small and variable.

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