In recent years, the phenomenon of premature aging in some cotton fields has aggravated. The premature aging of cotton has become the main factor restricting the further increase of cotton yield in our province. According to the 2010 survey results, premature aging of cotton can reduce production by about 15%, and when serious, it can reach more than 20%. At the same time, the quality of cotton also declines in different degrees, which affects the price of cotton and reduces the benefits of cotton cultivation. Analyzing the cause of premature aging of cotton, and proposing targeted solutions, is of great significance in improving the level of cotton production. I. Symptoms From the end of July to mid-August, under the condition of high temperature and drought, the top leaves and veins of cotton gradually lost their green color and turned to reddish-brown or reddish-brown. The leaves began to brown and dry in mid-August, and the lighter ones reduced the yield by 5%. ~15%, severe cases reduce production by more than 20%. Second, the incidence of low-lying, high groundwater level, a large number of water within the irrigation period or by the spider mites, locusts serious land damage prone to premature aging; soil compaction, poor permeability, poor root development, the root distribution of shallow root causes a small amount of late Premature senescence occurs in hairy and undergrowth cotton fields; premature aging of cotton fields with short cropping time occurs later and symptoms are lighter. Third, the impact of cotton growth in the late growth of malnutrition, detoxification in the late or nutrient growth caused by premature aging. In the late growing period of cotton, in the event of adverse weather conditions such as high temperature and drought, cotton root activity is reduced, and the resistance to stress is weakened. After the drought in late June followed by autumn drought, if the amount of rainfall is too low, the long duration of high temperature is harmful to the growth of cotton. A considerable part of the cotton fields will fall from the fallen leaves at this stage, and the yellowish wilt disease will be aggravated, causing premature aging to accelerate. The cotton field in cotton fields with low soil fertility is insufficient, and autumn peaches are not filled up, and it is prone to premature aging. The cotton fields with partial nitrogen and phosphorus fertilizers are associated with severe shortage of potassium and withering, and the input of flower and bell fertilizers is insufficient. The cotton itself lacks the ability to grow late, especially Is premature hair cotton fields, because sitting earlier peach, heavy load, if you do not pay attention to the late water and fertilizer inputs, more prone to premature aging. Fourth, preventive measures 1. Late-onset weak long-term prevention. In the application of organic fertilizer, straw returned to the field, deep plowing on the basis of deep loose. For soil compaction and poor permeability cotton fields, the cotton seedlings shall be ploughed in time as soon as possible and then cultivated twice every 10 days for a total of 3 times of cultivating, and the soil shall be loosened, preserved, and warmed to accelerate the growth rate of cotton. 2. Premature prophylaxis type prevention. According to the status of soil nutrients and the characteristics of the varieties, the balanced fertilization technique will be promoted so that the nutrients needed for each growth period of cotton can be supplied in a timely, sufficient, and balanced manner. Rational irrigation, adhere to the head water to see the sky, see the land, see the seedling growing, spotting drought, spot irrigation, delaying irrigation without delaying the plot, grasp the principle of seeing flowers irrigation headwater, irrigation should strictly control the amount of water in order to ensure the field The principle of moist and non-drought is not stopped. In late August, water will be stopped according to the growth potential of cotton seedlings. The combination of promotion and control to promote cotton root development is the key to effective prevention and treatment of premature aging under high-density conditions. Grasping the characteristics of rapid decline in soil moisture content in Shenglei and early flowering stages, appropriately controlling water and fertilizer, further promote deep rooting of cotton, coordinate the relationship between reproductive growth and vegetative growth of cotton, and enable photosynthetic products not only to meet the needs of roots and leaves, but also Can meet the needs of a large number of flowering bells; make the leaves of moderate size, dark green leaves, fruit branches have a certain ability to compensate. 3. Imbalance prevention of premature aging type. Further strengthen the field management, view the appearance of cotton in the middle growth period, and topdress the flower and bell fertilizer (8 to 10 kg/mu of compound fertilizer), and apply 80 g/mu of EM to the leaf surface every 10 days. Add dihydrogen phosphate. 150g/mu of potassium, 500g/mu of urea, and 40kg/mu of water were mixed and sprayed about 3 times. When the control of insects such as spider mites was achieved, the above three kinds of foliar fertilizers could be mixed with insecticides. , Can play both pest control and leaf fertilizer recovery time saving and double effect. 4. Prevention of premature aging of lesions. Reasonable rotation and downfall, deep ploughing and soil improvement, autumn ploughing and winter irrigation, improving the ecological environment of cotton fields. Select disease-resistant varieties, create a reasonable growth environment, reduce the impact of adverse environmental factors and increase the disease; rational application of potash fertilizer to increase the disease resistance of cotton plants, thereby increasing the yield and quality.
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