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Title: ELEVATED CO2 ON SORGHUM GROWTH AND YIELD AT HIGH AND LOW SOIL WATER CONTENT

Author
item OTTMAN, M - UNIV OF ARIZONA
item Kimball, Bruce
item Pinter Jr, Paul
item Wall, Gerard - Gary
item VANDERLIP, R - KANSAS STATE UNIV
item LEAVITT, S - UNIV OF ARIZONA
item LAMORTE, R - USDA-ARS-USWCL, PHOENIX
item MATTHIAS, A - UNIV OF ARIONZA
item BROOKS, T - UNIV OF ARIZONA

Submitted to: New Phytologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/10/2000
Publication Date: 3/15/2001
Citation: Ottman, M.J., Kimball, B.A., Pinter Jr, P.J., Wall, G.W., Vanderlip, R.L., Leavitt, S.W., Lamorte, R.L., Matthias, A.D., Brooks, T.J. 2001. Elevated co2 on sorghum growth and yield at high and low soil water content. New Phytologist. 150:261-273.

Interpretive Summary: The atmospheric carbon dioxide (CO2) concentration is expected to rise by 50% near the middle of this century. Therefore, a 2-year experiment was conducted to determine the effects of such a CO2 increase on the growth of field-grown sorghum using free-air CO2 enrichment (FACE) at ample (Wet) and limiting (Dry) levels of irrigation water. Grain yield tended to increase about 20% because of the elevated CO2 under the Dry conditions, but there was little effect at ample water or even a slight decease. Thus, these data suggest that future sorghum yields are likely to increase from rain-fed fields that normally tend to experience drought during the growing season, but irrigated sorghum or that grown in high-rainfall areas will likely be little affected by the CO2 increase. Such information is needed to develop future grower management strategies, and it will benefit all consumers of products such as sorghum flour and sorghum-fed chicken.

Technical Abstract: The atmospheric CO2 concentration is expected to increase by 50% near the middle of this century. An experiment was conducted to determine the effects of such a CO2 increase on growth and development of field- grown sorghum using Free Air CO2 Enrichment (FACE) at ample and limiting levels of irrigation water at Maricopa, AZ. The daytime CO2 concentrations were 561 and 368 umol/mol for the FACE and control treatments, respectively, averaged over the two years of the study. Irrigation plus precipitation averaged 1132 mm for the wet plots and 396 mm for the dry plots. Stover yield responded similarly to CO2 and averaged 848 g m-2 for the control and 928 g m-2 for FACE. In the dry plots, grain yield increased because of elevated CO2 from 472 to 553 g m-2 in 1998 and 106 to 142 g m-2 in 1999. In the wet plots, however, grain yield was not influenced by elevated CO2 in 1998, but decreased because of elevated CO2 from 476 to 424 g m-2 in 1999. Sorghum phenological development was not affected in a consistent manner by elevated CO2. Elevated CO2 had the general effect of slowing growth of the dry plots and accelerating growth of the wet plots during the vegetative stages, but causing the reverse after anthesis during grain fill. Leaf senescence was accelerated in the wet plots and may have been partially responsible for the lack of grain yield response to CO2 with ample water. In water-stressed sorghum, stomatal closure due to elevated CO2 has a negative effect on growth early, and only later in the growth cycle are the positive benefits of soil water conservation realized.