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Carbon Dioxide Uptake by Wide‐Row Grain Sorghum Computed by the Profile Bowen Ratio 1
Author(s) -
Allen L. H.,
Hanks R. J.,
Aase J. K.,
Gardner H. R.
Publication year - 1974
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1974.00021962006600010010x
Subject(s) - bowen ratio , atmospheric sciences , flux (metallurgy) , shading , sorghum , energy balance , environmental science , physics , agronomy , chemistry , sensible heat , thermodynamics , biology , art , organic chemistry , visual arts
A method for computing CO 2 uptake by an irrigated crop of wide‐row grain sorghum ( Sorghum bicolor (L.) Moench, var. ‘RS‐610’) was devised from measured profiles of temperature, water vapor, and CO 2 over the crop. The crop Bowen ratio, β and the ratio of photochemical heat flux density of carbon dioxide fixation to latent heat flux density, α, were determined from profiles of points, rather than from just two points. We call this method the profile Bowen ratio. The parameters α and β were used with the energy balance equation to compute the flux density of CO 2 to the crop as a function of solar radiation, which itself was a function of time of day. CO 2 flux density plotted as a function of solar radiation (or time of day) was lower at the highest radiation loads (midday) than at 1000 or 1400 hours. The lower CO 2 flux density at midday may be the result of more mutual leaf shading in this crop geometry at high solar elevation angles. The CO 2 flux density curve also showed concave curvature at the radiation loads concomitant with early morning and late afternoon hours when much of the solar energy was penetrating to ground in this east‐west row crop. Finally, computed daily CO 2 fluxes were reasonably close to the CO 2 equivalent of dry matter accumulation rates plus estimated respiration.