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Rice Cultivar Responses to Atmospheric CO2 Enrichment
Hasegawa, T., Sakai, H., Tokida, T., Nakamura, H., Zhu, C., Usui, Y., Yoshimoto, M., Fukuoka, M., Wakatsuki, H., Katayanagi, N., Matsunami, T., Kaneta, Y., Sato, T., Takakai, F., Sameshima, R., Okada, M., Mae, T. and Makino, A. 2013. Rice cultivar responses to elevated CO2 at two free-air CO2 enrichment (FACE) sites in Japan. Functional Plant Biology 40: 148-159.

In regard to the major crops of the world, the authors write that "the annual rate of yield increase has slowed over the past few decades (Bruinsma, 2009)," but they note that the demand for food is rising, "mainly due to the increasing population." As a result, they state that "the production of major crops will need to increase by 70% by 2050" - again citing Bruinsma (2009) - in order to "meet the growing demand for crops." And they add that "these production increases must be achieved under changing climate conditions," correctly concluding that "crop improvement programs must take these changing conditions into account."

What was done
Working in Japan with four cultivars of rice (Oryza sativa) at Shizukuishi in 2007 and 2008, and with eight cultivars at Tsukuba in 2010, Hasegawa et al. employed free-air CO2 enrichment or FACE technology to assess the effects of atmospheric CO2 enrichment to approximately 200 ppm above ambient - applied each day of the growing season from sunrise to sunset - on rice panicle density, spikelets per panicle, spikelet density, percent of ripened spikelets and single-grain mass, all under the real-world weather conditions that prevailed at these times and places.

What was learned
The eighteen researchers report that the range of final CO2-induced yield enhancements of the several rice cultivars ranged from 3 to 36%; and they say that "all of the tested yield components contributed to this enhancement."

What it means
The fruits of Hasegawa et al.'s labors clearly indicate the extreme importance of concentrating rice breeding efforts on cultivars that have strong positive responses to rising atmospheric CO2 concentrations, because without the help of this highly effective aerial fertilizer, we have little hope of being able to meet the 70% increase in crop yields that will be needed to feed the people of the world a mere 37 years from now. And for the same reason, breeders of all of the other major food crops of humanity should be pursuing the same course of action as well. In addition, it should be clear to all that we really need the extra CO2 that is being pumped into the air by our burning of coal, gas and oil.

Bruinsma, J. 2009. The resource outlook to 2050: By how much do land, water use and crop yields need to increase by 2050. In: Technical Papers from the Expert Meeting on "How to Feed the World in 2050." Food and Agriculture Organization, Rome, Italy.

Reviewed 24 July 2013