Studies On Population Structure Of High-Yield Cotton And Its Nitrogen Regulation

Improving cotton yield is the main purpose of cotton production, planting density and nitrogen fertilizer rate are main cultivation control to achieve high yield. On the basic of screening out high yield cultivars, the study on the effect of planting density and nitrogen fertilizer rate on physiological mechanism and fiber quality formation of high yield cotton cultivars could provide theory evidence for determining appropriate planting density and nitrogen fertilizer rate of Jiangxi cotton region. Field experiments were conducted to select high-yield cultivars which are suitable for Jiangxi cotton region in2007-2008in Jiangxi cotton region which is at the middle reach of Yangtze River Basin, Xiangzamian8and Ganmianza1were been selected. Field experiment were conducted to study the cotton economical character, dry matter, nutrient, yield, fiber quality in Jiujiang, Jiangxi in2008, by setting6plant density (12000,21000,30000,39000,48000, and57000plant/hm2) and6nitrogen fertilizer rates [N1:0, N2:150, N3:300, N4:450, N5:600kg/hm2, and N6:279kg/hm2+organic fertilizer (fowl dung)1500kg/hm2(which nitrogen, phosphorus, potassium nutrient are equal to N3)]. These experiments are conduct to research the best planting density and nitrogen fertilizer rate in Jiangxi Province. The main results are as follows:1. Cotton (Gossypium hirsutum L.) cultivars screening for high yield in Jiangxi regionStatistical analysis of yield and fiber quality data in2007and2008showed that Ganmianza1, Zhongchangza04, Ganmianza11and Xiangzamian8were the optimum cultivars to plant in Jiangxi. The results provided solution for cotton cultivar problem in Jiangxi province and provided theoretical basis for Jiangxi high cotton yield demonstration project.2. Effect of planting density on physiological mechanism, yield and fiber quality formationAs plant density increased, cotton growth period extended, fruit branch layer numbers and leafy shoots dropped off, LAI increased, plant height increased and then declined, dry matter accumulation per plant decreased, distributive indices of biomass in reproductive organ increased and then declined, the number of boll per cotton plant and boll weight cut down obviously, yield and net income appeared to have a decline trend after an initial ascent. According to the results and practical production, the best planting density for Jiangxi cotton region was between30000and39000plant/hm2, practical optimal plant density for yield and quality could increase or decrease depend on weather condition.3. Effect of nitrogen rate on physiological mechanism, yield and fiber quality formationAs nitrogen fertilizer rates increased, cotton growth period postponed, plant height and leafy shoots increased, pre-frost flowering rate decreased, dry matter and nitrogen content per plant increased, nitrogen use efficiency decreased, the number of boll per cotton plant, seed cotton and lint yield, output value and benefit all appeared to have a decline trend after an initial ascent. Compared with N3and N4, organic manure mating with chemical fertilizer (N6) had litter gap in growth period and plant height, but, ultimate output was highest on the condition of N6because dry matter, nitrogen content per plant and nitrogen use efficiency were highest. So, nitrogen fertilizer rate between300and450kg/hm2was best for Jiangxi province, and, organic manure mating with chemical fertilizer was better than chemical fertilizer alone when they have the same nutrient content.