Submitted to: Agricultural Meteorology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 1996
Publication Date: N/A
Interpretive Summary: In order to determine the consequences of global environmental changes on the security of world food production, efforts are underway to determine the growth and other physiological responses of major food crops to changing environmental factors. These global changes especially include the increasing concentration of atmospheric carbon dioxide (CO2) which is expected to double sometime during the next century. To determine whether such elevated CO2 would change growth, yield, water use, and other aspects of wheat and cotton production, experiments have been conducted under open-field conditions using a new technique called free-air CO2 enrichment (FACE). This paper presents results of these measurements, revealing for example that cotton growth was increased about 40% and wheat growth about 20%. This work will lead to more accurate modeling of future crop growth, which will help optimize management strategies and, of course, should ultimately benefit all future food consumers.
In order to determine the effects of the increasing atmospheric CO2 concentration on future crop productivity and water requirements, free-air CO2 enrichment (FACE) experiments at 550 micro mol/mol CO2 have been conducted in an open field at Maricopa, Arizona, U.S.A., on cotton (Gossypium hirsutum L., cv. Deltapine 77) and wheat (Triticum aestivum L. cv. yecora Rojo) crops at ample (Wet) and limiting (Dry) levels of water supply. With ample water, canopy net photosynthesis rates of cotton and wheat crops increased about 30-40%, with little evidence of down-regulation. Under the Dry treatment, the stimulation was about the same for cotton but much larger for wheat. Cotton growth was stimulated about 30% at both Wet and Dry water levels, with lint yield being stimulated even more, up to 80% under Wet and 50% under Dry. Wheat growth was stimulated less than that of cotton, about 20% at mid-season. Moreover, the final wheat grain yields increased only about 10% under Wet, whereas under Dry, the increase was about 20%. The FACE treatment had very little effect on the water use of cotton, but, for wheat, there appeared to be a small (4%) but significant reduction in water use, as determined by the soil water balance. Water use efficiency increased because of the larger growth and yeilds.