A Comparison of Scenarios for the Effect of Global Climate Change on Cotton Growth and Yield

Abstract

If global surface temperatures change as projected because of radiative and physiological effects of a changing environment, we should expect important changes in crop production in the 21st Century. Experiments were conducted at ambient and twice ambient atmospheric CO₂ concentrations at five temperatures. The 1995 temperature in Mississippi was used as a reference with the other temperatures being 1995 minus 2˚C, and 1995 plus 2, 5 and 7˚C. Daily and seasonal variation and amplitudes were maintained. Seedlings had 4–6 times as much leaf area and dry weight at 20 d after emergence when grown at 28˚C as at 23˚C (1995 ambient) average temperature during that growth period. Number of days to first square, flower, and open boll decreased as temperature increased. Double atmospheric CO₂ did not affect these developmental rates. Temperatures above 28˚C, or 1995 average whole-season temperatures, were detrimental to mid- and late-season boll retention and growth. No fruits were retained to maturity at 1995 plus 5 or 7˚C. However, whole season vegetative growth was not significantly reduced by temperature 5–7˚C above the 1995 ambient conditions. Twice ambient CO₂ caused about 40% increase in vegetative dry matter accumulation across temperatures. In a separate experiment, similar results were obtained on fruiting cotton grown at a range of temperatures based on long-term average US Midsouth July temperatures. Therefore, if global warming occurs as predicted, food and fibre production in such high-temperature and humid environments may be more limited to vegetative structures and the animals that consume vegetative structures.