Effects of Elevated CO2 on Crop Water Relations
Burkart, S., Manderscheid, R., Wittich, K.-P., Lopmeier, F.J. and Weigel, H.-J. 2011. Elevated CO2 effects on canopy and soil water flux parameters measured using a large chamber in crops grown with free-air CO2 enrichment. Plant Biology 13: 258-269.
Averaged across the two rotation cycles, Burkart et al. determined that the approximate 47% increase in the air's CO2 content they supplied to portions of the field reduced canopy stomatal conductance by 9%, 17% and 12% in barley, sugar beet and wheat, respectively, and that it likewise reduced canopy transpiration by 9%, 18% and 12% in the same three crops. And as a consequence of the lower canopy transpirational water loss, they found that the CO2 increase "increased plant water available soil water content in the course of the season by ca. 15 mm ... for all crops and years."
In discussing the implications of their findings, the five German scientists say the cumulative increase of soil moisture due to CO2 enrichment found in their study suggests that in a future atmosphere, "CO2-related water savings may improve crop water status and reduce the need for irrigation in Central Europe," which could prove a huge boon to the inhabitants of the continent.