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The purpose of this study was to evaluate current and obsolete cotton ( Gossypium hirsutum L.) cultivars and determine the rate of gain in cotton yields in Mississippi. We evaluated 17 cultivars on a Bosket sandy loam (fine‐loamy, mixed, thermic, Mollic Hapludalf) over a 2‐year period (1978 and 1979) to determine what genetic improvements the new cultivars had over the older ones. The study was comprised of two recently released cultivars (‘Stoneville 825’ and ‘DES 56’), 14 obsolete cultivars, and ‘Stoneville 213’. Stoneville 213 was released in 1962 but still accounts for approximately 12% of the cotton acreage in Mississippi. The two recently released cultivars produced significantly higher yields than the other cultivars. The obsolete cultivars produced 100 to 700 kg/ha less lint than the cultivars currently grown. The average rate of yield increase from 1910 through 1979 due to cultivar improvement was found to be 9.46 kg/ha/year. A regression analysis of the average lint yields in Mississippi from 1910 through 1979 shows that yields have actually increased at the rate of 8.62 kg/ha/year. Since 1965 yields have gradually decreased in spite of a genetic potential for increased yield. These data substantiate the fact that the inherent yielding ability of cultivars is not responsible for declining yields.
Bridge et al. (Thu,) studied this question.