Paper Reviewed
Bunce, J. 2017. Using FACE systems to screen wheat cultivars for yield increases at elevated CO2. Agronomy 7: 20, doi:10.3390/agronomy7010020.

Introducing the rationale for his work, Bunce (2017) notes that "the CO2 concentration in the atmosphere continues to increase rapidly, and may increase yields of C3 crops, helping to meet the expected increased demand for agricultural products." However, he notes that there can be a high degree of intraspecific variation in the yield responsiveness of such crops to CO2 enrichment, adding that "such variation could allow the achievement of larger field yield increases as CO2 rises, if new cultivars could be developed to better exploit the rising CO2." And thus he conducted an experiment to determine the yield response of several wheat cultivars to atmospheric CO2 enrichment.

His work was conducted at the South Farm of the Beltsville Agricultural Research Center in Beltsville, Maryland, USA. In the first of two experiments, Bunce grew four locally adapted wheat cultivars (Jamestown, Choptank, Pioneer 25 R40 and Pioneer 25 R32) in an area-distributed Free-Air CO2 Enrichment (FACE) system, which system "is designed to reduce the horizontal variation in mean CO2 compared with perimeter ring FACE systems." The wheat plants were grown in two consecutive growing seasons in 2013 and 2014 under an average ambient CO2 concentration of 422 ppm and elevated CO2 concentration of 628 ppm. In the second of his two experiments, using the same FACE system, Bunce grew an additional nine wheat cultivars during the 2015 growing season. And what did the two experiments reveal?

Not surprisingly, there was a great deal of variation in the yield responses of the wheat plants under both ambient and elevated CO2 conditions (ten cultivars experienced yield increases and three cultivars showed yield decreases). Quantitatively, those responses ranged from an 18 percent decline all the way to a positive 55 percent increase in mean seed yield in response to the 206 ppm CO2 increase.

Commenting on his findings, Bunce writes that "identification of lines with larger yield increases at elevated CO2 is only a first step to improving the response of a crop species to future CO2 conditions," noting that identification of traits responsible for those yield differences would be an important "next step toward selecting crops for future CO2 environments."