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Cotton planting population was an important factor, which decided to light in the distribution conditions. Excessive cotton planting population, lack of light in groups, group structure could deteriorate, thus affecting the population of dry matter accumulation, thereby affecting the quality of cotton boll. The study on effects of cotton planting population on the formation of cotton boll quality provided a theoretical basis for determining the appropriate cotton planting population, improving the field environment and the quality of cotton boll. In this study, we choose two cotton cultivars (Kemian 1, NuCOTN) for the field experiments carried out in Nanjing (118°50’E,32°02’N, Middle Lower Reaches of Yangtze River Valley) and Anyang (114°13’E,36°04’N, Yellow River Valley), which stand for the cotton planting population.The study focused on:(1) Effects of cotton planting population on the formation of cotton fiber quality. (2) Effects of cotton planting population on cottonseed biomass, fat and protein content.The main results were as follows:1. Effects of cotton planting population on the formation of cotton fiber qualityFiber length, fiber maturity and fiber micronarie with the cumulative dynamic of days post anthesis and the cotton planting population of the dynamic response of the trend was basically consistent and both showed highly significant negative correlation. Fiber fineness increased with days post anthesis decreased gradually acquired, and with a positive correlation between cotton planting population. With the increase of cotton planting population, fiber strength changed according to a parabolic curve. The highest fiber strength was obtained at 3.3×105plants ha-1 in Nanjing and 5.1×105plants ha-1 in Anyang, respectively. The too low or too high cotton planting population was not conducive to the formation of high-strength fiber. High cotton planting population is particularly vulnerable. Variety, site, and flowering period had no significant effect on the trends of fiber quality formation and response to cotton planting population. It was most favorable to improve the fiber quality that suitable cotton planting population. The impacts of cotton planting population on fiber quality were closely related in canopy light conditions.2. Effects of cotton planting population on cottonseed biomass, fat and protein contentUnder the conditions of cotton planting population, the cumulative process of cottonseed dry weight per boll, cottonseed biomass and fat content met Logistic growth curve. As cotton planting population was increased, initial and termination date of speedy accumulation of cottonseed dry weight per boll, cottonseed biomass and fat content came early; the duration for speedy accumulation was shorten, accumulation rate, theoretical maximum values were reduced. Cottonseed dry weight per boll, cottonseed biomass and fat content were strongly negatively correlated with cotton planting population at both experimental sites and flowering dates. However, the cumulative process of cottonseed protein content was similar to "V" for each treatment. A highly significant quadratic relationship was shown to exist between cottonseed protein content and cotton planting population for varieties, sites, and flowering dates. The highest cottonseed protein content was obtained at 3.3×105 plants ha-1 in Nanjing and 5.1×105 plants ha-1 in Anyang, respectively. Variety, site, and flowering date had no significant effect on the trends of cottonseed dry weight per boll, cottonseed biomass, fat and protein content. The impacts of cotton planting population on cottonseed quality were closely related in canopy light conditions. Low cotton planting population helped the improvement of cottonseed dry weight per boll, cottonseed biomass and fat content, while the too high or too low cotton planting population was not conducive to cottonseed protein synthesis and accumulation.
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