Climate Fact: Cotton Yields and Climate
A common cotton disease in the southeast, hardlock, is caused by fungus that is sensitive to changes in temperature and humidity. The disease does better during years when humidity and rainfall levels are above average, especially during the months of July to September, when cotton plants flower and bolls (pods containing 32 seeds from which the cotton fibers grow) mature. In Florida, during the wet and humid year of 2002, hardlock caused crop yields to decrease from 650 pounds per acre to 400, or the equivalent of 20 million dollars in lost yields. Drier and less humid years, on the other hand, discourage fungal growth and favor high yields. Over 50 percent of the variability in yields in the southeastern U.S. can be explained by climate. Years with the highest cotton yields correspond to years with lower than normal sea surface temperatures (SSTs) in the Gulf of Mexico and Atlantic Ocean, where the winds that blow into the southeast during the summer originate. Lower SSTs mean less humidity, and cause relatively dense air to become concentrated in upper level air masses, which discourages convective cloud formation and rainfall.
Seasons: Summer, Fall
Sources: Baigorria, GA et al. “Assessing Predictability of Cotton Yields in the Southeastern United States Based on Regional Atmospheric Circulation and Surface Temperatures.” Journal of Applied Meteorology and Climatology 47 (2008): 76-90 and The University of Florida Education and Research Center. “Cotton/Hardlock.” Accessed Online 1 October 2008
