Cotton yield progress - why has it reached a plateau?

encing severe economic stress. Relief will come in the form of higher commodity prices, lower production costs, and higher yields. Some progress in improving fiber quality and reducing expensive production inputs has been made. However, further improvements need to be associated with yield increases. Yields of most field crops have been increasing during the last several decades. Average U.S. cotton yields per acre are indicated in Figure 1. The yield curve from 1961 to about 1999 indicates an average increase of 5.99 lb/A/year. However, inspection of the yield curve shows a plateau from 1961 to 1979. This was followed by 10 years of increasing yields/A, as a result of better insect control, crop management, and the introduction of new germplasm into breeding programs. However, quadratic analysis of the yields from 1980 to 1999 shows that yields peaked in about 1992 (Figure 2). Dr. Hal Lewis, an independent cotton breeder working with the American Cotton Producers Association, analyzed cotton yield trends and reached a similar conclusion. He also showed that the year to year variation within the last 20 years, is four times greater than within the previous 20-year period. Figure 1 shows the great year to year variation. What are the major factors impacting yield? They include weather, management, rise of new pests, and variety improvement. Weather. Certainly year to year variability has a big impact on yield, but is it responsible for the yield plateau? Abnormal weather would need to cover the entire Cotton Belt from Carolina to California. Such weather patterns also would have to negatively affect other major crops. Weather scientists have indicated that the earth’s climate has gradually been getting warmer. Higher temperatures could have plus and minus effects U . S . C O T T O N B E LT