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Atmospheric CO2 Enrichment and the Growth of Corn Under Various Degrees of Water Stress
Chun, J.A., Wang, Q., Timlin, D., Fleisher, D. and Reddy, V.R. 2011. Effect of elevated carbon dioxide and water stress on gas exchange and water use efficiency in corn. Agricultural and Forest Meteorology 151: 378-384.

What was done
Corn plants were grown from seed in naturally-sunlit soil-plant-atmosphere-research (SPAR) units in which temperature, humidity and CO2 concentration were precisely controlled, the latter at either 400 ppm (ambient) or 800 ppm (elevated), beginning 21 days after emergence (DAE). These units were placed atop soil bins (2.0 m long by 0.5 m wide by 1.0 m deep) that were filled with a mixture of 75% coarse sand and 25% vermiculate, where soil water contents were monitored hourly by a time domain reflectometry (TDR) system that consisted of 15 TDR probes per chamber placed within three rows at depths of 0, 15, 30, 50 and 75 cm from the soil surface. By means of this system of soil water content assessment, combined with nightly "fertigation," Chun et al. were able to provide the plants with the nitrogen they needed while maintaining four different soil water stress levels -- control, mild, moderate and severe -- which were also initiated 21 DAE. Thereafter, the height, number of leaves, leaf lengths and growth states of the corn plants were determined twice weekly, while samples of the plants were collected, dried and analyzed for biomass accumulation at 21 and 60 DAE (the beginning and the end of the different CO2 and soil water content treatments).

What was learned
The five researchers determined that under both well-watered and water-stressed conditions, higher soil water contents were maintained in the elevated CO2 treatment, even though 20-49% less water was applied to the soil of the elevated CO2 treatment. Their study did not, however, provide any evidence that the elevated CO2 treatment had a strong effect on plant height, leaf area or above-ground biomass. But the water saving was amazing; and as a result ...

What it means
... they concluded, that "under increased CO2 concentrations as generally predicted in the future, less water will be required for corn plants than at present." And since water is already a scarce commodity in many parts of the world -- and will only become more scarce, more expensive and more difficult to obtain in the days and years ahead -- this finding is extremely welcome news.

Reviewed 6 April 2011