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This article in AJ

  1. Vol. 68 No. 1, p. 30-35
     
    Received: July 26, 1975


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doi:10.2134/agronj1976.00021962006800010009x

Reflectant Induced Modification of Soybean Canopy Radiation Balance. III. A Comparison of the Effectiveness of Celite and Kaolinite Reflectants1

  1. Raoul Lemeur and
  2. Norman J. Rosenberg2

Abstract

Abstract

Soybeans (Glycine max L. ‘Amsoy’) were coated with Celite and kaolinite reflectants to increase reflection and reduce net radiation. Such treatment is intended to decrease evapotranspiration and improve water use efficiency. The study was undertaken to establish the specific reflection patterns at various wavelengths of reflectorized soybeans. The effectiveness of the materials aid the influence of additional applications applied factorially during the growing season was also evaluated. Both reflectant materials are most effective in the waveband of photosynthetically active radiation (PAR: 400–700 nm). Reflection coefficients in this waveband were double that from a natural canopy. The effect on near infrared radiation (NIR: 750–1,550 nm) was small. The average increase in shortwave reflection (300–3,000 nm) ranged from 10 to 20%. Reduction of net radiation measured over the treated canopies ranged from 5 to 10%. Within the treated canopies net radiation was greater than in the untreated crop. Application of reflectants at the beginning of the growing season was more effective in increasing reflection and reducing net radiation than were applications at later stages of crop maturity. The effects of additional treatments as the crop developed were not cumulative. Therefore additional applications should be made only to maintain the quality of the coating. Celite is the more effective material, producing the same degree of reflection with half as much material as is required when kaolinite is used.

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