A Study On The Characteristics Of Architecture Of Cotton Population And The Control Methods In The Sub-suitable Area Of The Northern Part Of Xinjiang

Plant architecture can reflect the productivity of plant. In this paper, the characteristics of morphological plasticity, foliage distribution pattern and the dynamics of stem and leaf growth were studied. The characteristics of high-yield architecture of cotton population and the regulation methods were analyzed. The main results are as follows:1. The spatial characteristics of cotton populationThe performances of cotton population taking full advantage of environmental resources are such as good way in growth, fully occupation of space, active responses of stem and leaf to solar radiation and different space, among which the most obvious sign is the structure formed by cotton population.(1) When cotton plants can occupy different spaces and have different growth rates at different growing satges, they tended to form high-yield population structure. This experiment showed that when population density was 5×10⁴/hm², cotton plants grew quickly and the population yield was high. The maximum increment of LAI per day was 0.156 in the bud stage of cotton. The biggest increment of the sum of internodes per day was 1.5cm from the beginning to the peak of bud stage. The increment of LAI per day was 0.092 from the blooming period to the wadding stage. When population density was 25.6×10⁴ /hm², the cotton was growing slowly but the population yield was high too. The maximum increment of LAI per day was 0.03 at the bud stage. The biggest increment of the sum of internodes per day was 1.4cm from the beginning to the peak bud of stage. The increment of LAI per day was 0.012 from the blooming period to the wadding stage.The degree of morphological plasticity might be used to infer the critical period for cotton growth. When morphological plasticity showed biggest degree, it might be regarded as the critical period for cotton growth. The morphological plasticity of leaf area of branch might be used to judge the cotton growth. If the leaf area of branch per cotton plant was not less than 720cm² at the wadding stage, the plant might be regarded as normal in growth.The relationship between the number of bolls and the leaf area of branch per cotton plant was y= -13.2424+3.10068ln(x), when the leaf area of branch per plant was between 720cm²-2000cm²; and y=2.7078+0.005182x-8.37148E-07x²+1.02373E-10x³, when the leaf area of branch per plant was more than 2000cm² (here, y: the number of bolls per plant; x: the leaf area of branch per plant).(2) When the stems and leaves could occupy the sparse space, the productivity per plant was high. When the distances between rows and plants were determined, the plants that grew quickly could occupy the space between rows by the growth of stems and leaves, whereas the plants that grew slowly tended to hedge the competition from the strong plants and grew in the sparse space. When the situations of illumination and ventilation were improved, the productivity increased.(3) When the leaf inclination angles, azimuth angles, angles between leaf and solar ray could adaptively respond to the solar radiation, the potential of productivity of cotton plant could be played. When at least two indices of leaf angles responded to the angles of solar radiation, cotton plant could bear more bolls at the peak boiling stage and the late boiling stage.(4) LAI dynamic trend before topping could be simulated by Lewis-Leslie model, which could be used as a reference for understanding the changes of the characteristics of cotton population.2. The structural characteristics of cotton populationWhen the stems and leaves of cotton plants formed certain spatial structures, solar radiation and carbon dioxide could be fully used.(1) Aggregate distribution of foliage. The relationship between the number of category of leaf assemblage and the scales was power exponential function. When there were more number of category of assemblage of leaves and layers, the number of bolls per plant tended to be more. When the range that met the relationship of power exponential function was broad, such as 7.3-28.4cm, and the initial value (i.e. the mean diameter of leaves) of the range was big, the plot yield tended to be high.(2) The fractal structure of foliage. When the values of fractal dimensions of single and population were big, such as D₀=1.751 or D₂=2.294, and the difference between them was small, and the scale invariant range was broad, such as 6.5cm-28.9cm for the single plant and 8.9cm-52.5cm the population, and the scale invariant range of the population was wider than that of single plant and the canopy breadth of single plant. the plot yield tended to be high.(3) The foliage distribution pattern. When the scales of distribution patterns of leaves of single plant and population were big, such as not less than 14cm for the pattern of number of leaves, and not less than 32cm for the pattern of leaf areas, the plot yield tended to be high. If there was a multi-scale pattern, the potential of productivity of cotton population tended to be played fully.(4) The canopy characteristics of single cotton plant. When the canopy width was broad, such as 68.7cm for the population with lowest density, and 32.9cm for the population with highest density, the vertical height of canopy is high at the peak boiling stage, such as 64cm for the population with lowest density, and 42cm for the population with highest density, and the changes of width and vertical height of canopy were small from peak boiling stage to late boiling stage, and crown shape ratio was about 1, there tended to be more bolls per plant.3. The control of growth of cotton plantThe main methods used to control the growth of cotton plants were water- and fertilizer-control methods.Since cotton plants were cultivated under plastic film mulch, if soil water storage or rainfall was enough during seedling stage, surface soil would contain too much water affeting the growth of root system. The coverage of plastic film increased the surface soil moisture, which inhibited the growth of root system deeply and decreased the drought-resistant ability of plants, and even damage the plants. In this case, irrigation should be carried out in advance. After hardening of seedlings, gradually increased irrigation helped cotton plants grow up from water-scarcity state to normal state of water demand. According to the stages of cotton growth, using three irrigation methods increased the leaf areas of the main stems and the branches, stem height, diameters of the stems, number of bolls and single boll weight.The effects of nitrogenous fertilizer to the growth of cotton was obvious in the initial period. The application of more nitrogenous fertilizer, such as 450kg/hm² for urea, promoted the growth of stem heights, leaf areas of the main stems and of branches at the initial period of cotton growth. The application of less nitrogenous fertilizer, such as 150kg/hm² for urea, the shedding of buds and fruits increased. The application of suitable amount of nitrogenous fertilizer, such as 300kg/hm² for urea, the falling of leaves decreased. When applying less amount of nitrogenous fertilizer at the late growing stage, promoted the growth of stem height and decreased the falling leaves.The application of phosphate fertilizer promoted the increase of leaf areas of the main stem at the bud period. At the blooming period, when applying phosphate fertilizer at the medium level, the leaf areas of the main stem increased, whereas when increased the application of phosphate fertilizer, the stem height increased obviously. When applying phosphate fertilizer at the medium level, the number of shedding buds, total leaf and green leaf of the main stems increased.At the present cultivation conditions, the following treatments might promote the yield of cotton: irrigation: 3500m³/hm² or 360mm water, population density: 5×10⁴ /hm² or 17.8×10⁴ /hm², nitrogenous fertilizer (urea): 300kg/hm², phosphate fertilizer (double superphosphate): 300kg/hm², DPC: 67.5g/hm², date of topping: from the beginning of blooming period to the peak blooming period.