Analysis of Effects of Atmospheric Carbon Dioxide and Ozone on Cotton Yield Trends

Abstract

Cotton (Gossypium hirsutum L.) yields have declined since 1964 despite improvements in technology and introductions of higher‐yielding cultivars. Cotton scientists have been unable to identify exact causes of the yield decline. For the past 25 yr, global atmospheric CO2 concentration ([CO2]) has been increasing due to the increased burning of fossil fuels; cotton has been found to be sensitive to [CO2]. Cotton has also been found to be sensitive to atmospheric ozone concentration ([O3]) at levels that occur regularly where it is grown. To analyze the effects of [CO2] and [O3] on cotton‐yield trends, simulations were made using the cotton crop model GOSSYM. Input data for simulations were obtained from cotton breeders' trial sites located at Florence, SC; Stoneville, MS; College Station, TX; Phoenix, AZ; and Fresno, CA. The simulated effects of the [CO2] and [O3] on cotton yields changed from location to location due to interactions with soil, plant, and atmospheric variables and with nutrient levels in the soil. Given enough N, the increased [CO2] would probably result in a 10% increase in lint yield. Due to N stress sometime during the growing season, however, the plants could not fully utilize the increased [CO2]. Ozone concentration increased during the period of cotton‐yield decline, and this increase in [O3] was found to affect simulated cotton yields adversely. It appears that O3 is one of the contributing factors to the yield decline. Overall O3 had a more adverse effe…