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Solar Radiation for Plant Growth

G. Szeicz
Journal of Applied Ecology
Vol. 11, No. 2 (Aug., 1974), pp. 617-636
DOI: 10.2307/2402214
Stable URL: http://www.jstor.org/stable/2402214
Page Count: 20
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Solar Radiation for Plant Growth
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Abstract

Analyses of theoretical calculations and experimental measurements show that the photosynthetically useful fraction of the solar spectrum, ηT, for the total (= direct + diffuse) radiation is almost independent of atmospheric conditions and is nearly constant at 0.50 ± 0.03. For the direct beam only, in very clean air in the winter ηI varies between 0.35 and 0.45 as solar elevation, β, increases from 10 to 45⚬; in the summer the range is smaller and is from 0.41 to 0.49 for the same range in β. For the diffuse radiation coming from the blue sky ηD is 0.75. The results are taken as evidence that ηT is so nearly constant that climatological measurements of solar radiation can be used confidently in estimating efficiencies of photosynthesis and crop growth in the field.

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