Relationship of Week of Flowering and Parameters of Boll Yield in Cotton1

Abstract

AbstractCotton (Gossypium hirsutum L.) experiments generally are reported in yield per unit area of land. This yield is a product of number of bolls per unit area and yield per boll. Estimates of yield per boll include an element of sampling. Our purpose was to relate week of flowering to the variability of boll yield components. Boll samples derived from 5 consecutive weeks (periods) of blooming in six diverse cotton cultivars in 1974 and 1975 were used to estimate the separate seed and fiber parameters that are components of boll yield. Seed yield per boll (SY/B) declined from the first through then fifth period of bloom, due to a significant loss in weight per seed ( g / S ) . Seed number (S/B) was lowest from first period fruit. Fiber yield per boll (FY/B) increased from the first to third period of bloom, but decreased sharply the last two periods. The weight per fiber (μg/f) was the main component to influence fiber yield adversely in late season bolls. The number of fibers per mm2 of seed surface showed a differential response for the two seasons over the bloom periods. Seed surface area (S.S.A./S) was influenced b bloom periods, cultivars and years. All components or FY/B gave significant year × period interactions. These data suggest that sampling should emphasize bolls derived from bolls set during the peak of flowering. Further implications of these results upon sampling technique in cotton research are discussed.