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Modeling Elevated Carbon Dioxide Effects on Water Relations, Water Use, and Growth of Irrigated Sorghum
Author(s) -
Grant R. F.,
Kimball B. A.,
Wall G. W.,
Triggs J. M.,
Brooks T. J.,
Pinter P. J.,
Conley M. M.,
Ottman M. J.,
Lamorte R. L.,
Leavitt S. W.,
Thompson T. L.,
Matthias A. D.
Publication year - 2004
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/agronj2004.1693
Subject(s) - sorghum , irrigation , environmental science , evapotranspiration , agronomy , canopy , carbon dioxide , water use efficiency , transpiration , deficit irrigation , water use , chemistry , hydrology (agriculture) , irrigation management , photosynthesis , botany , ecology , biology , biochemistry , geotechnical engineering , organic chemistry , engineering
Elevated concentrations of atmospheric CO 2 ( C a ) are believed to raise sorghum [ Sorghum bicolor (L.) Moench] productivity by improving water relations. In ecosys , water relations are simulated by solving for the canopy water potential (ψ C ) at which water uptake from a model of soil–root–canopy water transfer equilibrates with transpiration from the canopy energy balance. Simulated water relations were tested with ψ C , water uptake, and energy exchange measured under ambient (363 μmol mol −1 ) and elevated (566 μmol mol −1 ) C a and high vs. low irrigation in a free air CO 2 enrichment experiment during 1998 and 1999. Model results, corroborated by field measurements, showed that elevated C a raised ψ C and lowered latent heat fluxes under high irrigation and delayed water stress under low irrigation. Changes in ψ C modeled under ambient vs. elevated C a varied diurnally, with lower ψ C causing earlier midafternoon stomatal closure under ambient C a . Modeled changes in sorghum water status caused elevated C a to raise seasonal water efficiency under high and low irrigation by 20 and 26% (vs. 20 and 13% measured) in 1998 and by 9 and 27% (vs. 6 and 26% measured) in 1999. Ecosys was used to generate an irrigation response function for sorghum yield, which indicated that yields would rise by ≈13% for a range of irrigation rates if air temperatures were to rise by 3°C and C a by 50%. Current high sorghum yields could be achieved with ≈120 mm or ≈20% less irrigation water if these rises in temperature and C a were to occur.