How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic

Elevated CO2 Increases Yield in Water-Stressed Sorghum
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. and Brooks, T.J.  2001.  Elevated CO2 increases sorghum biomass under drought conditions.  New Phytologist 150: 261-273.

What was done
Sorghum (Sorghum bicolor L.) plants were grown in a FACE experiment conducted near Maricopa, Arizona, USA, within 25-meter diameter field plots.  Plants were fumigated with air containing either 360 or 560 ppm CO2 and were further subjected to irrigation regimes resulting in adequate and inadequate levels of soil moisture.  Thus, the authors studied the interactive effects of elevated CO2 and soil moisture on the growth and yield of sorghum, which is an important agricultural C4 crop in many parts of the world.

What was learned
Averaged over the two years of experimentation, elevated CO2 increased crop yield by 15% in the dry soil moisture plots, but had no effect on the yield of plants grown in plots receiving adequate levels of soil moisture.

What it means
As the atmospheric CO2 concentration continues to rise, it is likely that yields of sorghum will increase in areas that are subjected to drought and low levels of soil moisture, while little to no change will occur in regions where adequate soil moisture exists.  Under conditions of irrigated agriculture in the future, therefore, growers may be able to produce the same level of yield as today while applying less irrigation water.  Under such a scenario, the water saved could be used for other agricultural, environmental or urban purposes.  In addition, the results of this study demonstrate that C4 plants can -- and do -- respond to atmospheric CO2 enrichment, and that plant growth responses to elevated CO2 can often be greater under stressful, rather than non-stressful, growing conditions.