Effects Of Plant Density On Dry Matter Accumulation, Nutrition Uptake, Yield And Fiber Quality Of Hybrid Cotton

Improving cotton yield is the main purpose of cotton production, planting density is one of the regulating factors to the production and fiber quality of cotton. For improving yield and fiber quality through plant density, the effects of plant density on dry matter accumulation and nutrition uptake of different fruiting branches were studied in this research. In2009-2010, field experiments were carried out in Dongtai(120°07’E,32°33’N) and Dafeng(120°13’E,32°56’N), respectively. Two cotton cultivars (Kemian6and Xiangzamian8) were chosen, and six plant density (12000,21000,30000,39000,48000,57000plants/ha). The study focused on:(1) Effects of Plant Density on Yield and Fiber Quality of Hybrid Cotton;(2) Effects of Plant Density on Dry matter Accumulation and Distribution of Hybrid Cotton;(3) Effects of Plant Density on Uptake and Utilization of N, P and K of Hybrid Cotton. The main results were as follows:1Effects of Plant Density on Yield and Fiber Quality of Hybrid CottonThe number of fruiting sites and fruiting branches per plant, boll weight, as well as bolls number per plant were significantly decreased with plant density increased. But there was no significant difference in lint percentage between all treatments. The seed yield was the highest under the30,000plants/ha. High plant density reduced micronaire but did not affect the other cotton fiber quality. In addition, high plant density decreased the boll weight and bolls number on different fruiting branches, especially lower fruiting branches. Upper fruiting branches and middle fruiting branches produced higher contribution rate of yield than lower fruiting branches across treatments. Moreover there was no significant difference in fiber properties between different fruiting branches.2Effects of Plant Density on Dry matter Accumulation and Distribution of Hybrid Cotton Accumulative amounts of total dry matter in cotton plants were increased when plant densities were increased. The general pattern of cotton dry matter followed a logistic curve with the progress of growth. The eigenvalues of the dynamic accumulation model of dry matter accumulation was affected significantly by the planting density. And dry matter accumulation in the reproductive organs was the highest under the30,000plants/ha, the result showed highest direct effect on lint cotton yield. In addition, the accumulation of dry matter on LFB decreased at later growing stage, and fruiting branches senescence of cotton developed earlier and was more severe than MFB and UFB across treatments. A reduction in fiber yield would be caused by planting with excessive density.3Effects of Plant Density on Uptake and Utilization of N, P and K of Hybrid CottonAccumulative amounts of N, P and K in cotton plants were increased when plant densities were increased. However, N, P and K accumulation and nutrient economic coefficients in the reproductive organ exhibited a parabola function when plant densities were increased. And N, P and K accumulation and nutrient economic coefficients in the reproductive organ were the highest under the30,000plants/ha. In addition, the highest lint yield were1610.3kg/ha under the30,000plants/ha. The percent of N, P and K uptakes of cotton was the highest at the initial flowering up to peak flowering stage during the whole development stages, but the percent of N, P and K uptakes during the initial flowering to peak flowering stage was reduced when plant densities were increased. With plant densities increasing, the nutrient uptakes per100kg lint were increased, but the percent of K uptakes was reduced. Increased plant density enhanced N, P, and K content and accumulation of per plant in different fruit branches, but accelerated branches senescence, especially the lower branches. And the result was consistent with the weight of bolls in different fruit branches.