Thursday, May 5, 2016

Reason #48 Why I Love To Blog -- May 5, 2016

Back on May Day, I wrote:
Back in 1972, I spent a summer in Alaska -- Barrow, Alaska, to be precise -- at a laboratory there, studying the efficiency of Arctic grasses in utilizing CO2. It was understood that Arctic grasses were more efficient at utilizing CO2 than grasses (e.g., corn) in South Dakota.

The lead researcher felt that if one could transfer that efficiency to corn grown in Iowa, the average cornstalk would be one foot higher and produce six ears of corn instead of the average three for the same amount of soil, nitrogen, and water.
A reader sent me a table that showed just how much better wheat would do in a CO2-enriched environment. If one googles "wheat increased atmospheric CO2" one finds a gazillion articles on the subject. This is typical (for easier reading, I left out all the references; they can be found at the link):
Nearly all crops respond to increases in the air's CO2 content by displaying enhanced rates of photosynthesis and biomass production. Does the same hold true of Triticum aestivum, better known to most of us as wheat? Let's see what some of the atmospheric CO2 enrichment studies of the last few years have revealed about the subject.

In a FACE study conducted in Arizona, USA, wheat plants grown at 570 ppm CO2 exhibited enhanced rates of photosynthesis that led to approximately 8 and 16% more seasonal carbon uptake under low and high soil nitrogen conditions, respectively. Similarly, twice-ambient atmospheric CO2 concentrations stimulated rates of photosynthesis by 20 to 50%, depending upon the prevailing irradiance and temperature.

Because elevated CO2 stimulates rates of photosynthesis in wheat, it should also increase biomass and grain yield. And it does. In the Arizona FACE study, for example, the extra 200 ppm of CO2 increased grain yields by 17 and 14% in water-stressed and well-watered plants, respectively.
[Others] however, reported even larger CO2-induced yield stimulations in their open-top chamber experiment in response to a 300-ppm increase in the atmosphere's CO2 concentration: 54% vs. 40% for water-stressed and well-watered plants, respectively. Likewise, [another researcher] reported that a 550-ppm increase in the air's CO2 concentration increased the plant dry weight of wheat by 50 to 90%. In addition, twice-ambient CO2 concentrations have been shown to increase the grain yield of wheat by 13% and by 10-20%.
Moreover, various crop growth models applied to different climate change scenarios have predicted significant CO2-induced wheat yield increases in Bulgaria and Australia.
A doubling of the atmospheric CO2 concentration even increased the grain yield of wheat plants infected with a rust-causing fungus by 28 and 42% under conditions of ambient and elevated ozone concentrations.

On another note, [another researcher] reported that wheat plants grown at 550 ppm CO2 in the Arizona FACE experiment maintained more positive (less stressful) leaf water potentials than plants grown in air containing 370 ppm CO2.
Using this same experimental setup, Hunsaker et al. (2000) further noted that the water-use efficiency of CO2-enriched plants was 10 and 20% greater than that displayed by their ambiently-grown counterparts under low and high soil nitrogen regimes, respectively. In addition, [it was] reported that the CO2-induced increase in the water-use efficiency of wheat in their open-top chamber experiment was as high as 77%.

In summary, as the air's CO2 content continues to rise, wheat plants should display increasingly greater rates of photosynthesis and biomass production, which should lead to ever greater grain yields in this important cereal crop, even under conditions of low soil moisture or poor soil fertility.

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