Cotton Response to Rising Air Temperature and CO₂ Content

Noting that "responses to elevated CO₂ may differ at different temperature levels and that a potential reduction in yield due to high temperatures" is "very relevant," Yoon et al. (2009) grew well watered and fertilized cotton (Gossypium hirsutum L.) plants from seed to maturity -- one plant to each container of washed sand, with spacing between plants similar to the plant spacing found in typical cotton fields -- within the Georgia Envirotron (located at the University of Georgia Griffin Campus), where they were placed within chambers maintained at all combinations of two day/night air temperatures regimes (25/15°C and 35/25°C) and three atmospheric CO₂ concentrations (400, 600 and 800 ppm), during which time, as well as at the end of the study, various plant characteristics were measured.

In terms of final yield, Yoon et al. report that at the lower of the two air temperature regimes, "final boll weight at harvest was 1.59 times (at 600 ppm) and 6.3 times (at 800 ppm) higher compared to ambient CO₂," and they say that "increasing the temperature increased this difference, as the final boll weight was 34.1 times (at 600 ppm) and 23.3 times (at 800 ppm) higher compared to ambient CO₂." In addition, they state that "the response of final lint yield to CO₂ was more or less similar to the response of boll weight."

Both higher air temperatures and higher atmospheric CO₂ concentrations -- individually and in combination -- were a great boon to cotton productivity in this well-controlled study, demonstrating that in this experiment not only were the "twin evils" of the radical environmentalist movement not detrimental to cotton growth and development, they were almost unbelievably beneficial.