Analysis of Effects of Atmospheric Carbon Dioxide and Ozone on Cotton Yield Trends
1989
Reddy, V. R. | Baker, Daniel N. | McKinion, J. M.
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 effect on simulated cotton yields at locations where O₃ was present at higher concentrations, i.e., Phoenix, AZ and Fresno, CA. Contribution from the Dep. of Agricultural Engineering, Clemson Univ. and the USDA-ARS Crop Simulation Res. Unit, Crop Science Res. Lab.
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