At the beginning of flowering, cotton enters a period of vigorous fertility, requiring more fertilizer, more nitrogen, and greater intensity. From this time, the amount of nitrogen absorbed accounts for 60% of the nitrogen uptake during the whole growth period, and the phosphorus and potassium required during this period also account for More than half of the total. The principle of fertilization of high-yield cotton, on the basis of the base fertilizer, timely grasp the topdressing management. In recent years, the development trend of cotton high-yield cultivation management, under the conditions of systematic control, to increase the cotton planting density to achieve high-yield ways, this high-yield method is particularly prominent in Xinjiang cotton areas. In addition, in the Yangtze River Basin and the cotton planting area in North China, in order to ensure the continuous improvement of the total output of cotton and food crops, in recent years, there has been a trend of shortening the cotton growth period and vigorously developing summer cotton. For these two new developments, there must be corresponding new measures in the management of cotton topdressing.
In the past, the spring planting of cotton was the main focus, emphasizing the post-fertilization (mainly referred to as nitrogen fertilizer), and the goal was to strive for “three peachesâ€, that is, the cotton plant was required to be a high-yield plant with characteristics of peach vines, vines full waist and autumn peach tops. In the topdressing, the principle of reapplying the weight of the fertilization center and applying the topping fertilizer to the fertilization center was proposed. However, the situation is different now, and the period of topdressing should be adjusted forward. Under the control conditions of the reduced amine system, early bud and flower fertilizer have a good effect on the high yield of spring cotton, such as early enhancement of root activity. Therefore, the application of chemical control technology provides a guarantee for adjusting the time of topdressing. In the cotton field before the ridge is closed, it can reduce the mechanical damage of labor and cotton plants. Especially the summer cotton or short-season cotton must emphasize the early topdressing in the bud period. Cotton seedlings are early, reducing the threat of late maturity. In short, under the premise of adopting systematic control, the whole process of cotton fertilization is based on base fertilizer, and the principle of proper application of topdressing is applied. In recent years, cotton high-yield slab fields have shown that proper early topdressing is beneficial to root growth and premature root failure prevention under conditions controlled by ketamine. In general, it is feasible to apply the top dressing in combination with the bud stage (4~5 leaves) in advance of the topdressing stage of summer cotton. It is also feasible to carry out top dressing at the initial flowering stage (one or two young bells have been hung).
The topdressing in the bud stage or the early flowering stage is mainly to add appropriate nitrogen fertilizer (such as 10~15 kg/mu urea), in the potassium-deficient soil, the low effective potassium content (such as the sandy loess with strong sandy soil) or the base fertilizer. In the cotton field of potash and organic fertilizer, 5-6 kg of potassium chloride should be added. At this time, chasing potassium can promote the increase of cotton age. Especially for some plots of insect-resistant cotton varieties, the amount of potash fertilizer is higher than that of ordinary cotton varieties to meet the needs of high yield.
The application method of top dressing should be mixed with fertilizer and timely watering. Urea should not be applied to avoid loss of volatilization or fumigation of cotton leaves. In production, urea is often sprinkled on the surface and rain, neither covering soil nor timely irrigation. This method of application is unscientific.
In addition, for high-yield and super-high-yield cotton fields, if there is a weakening of the growth momentum or automatic capping in the late stage of cotton bolls, 5-8 kg of urea should be added in time to prevent the early decline of cotton plants for the autumn peach.
Cotton topdressing should be adapted to local conditions. The following principles and recommendations for topdressing application are proposed for the characteristics of different cotton producing areas in China:
In the Huanghuaihai cotton area, the amount of nitrogen and phosphorus fertilizer in the Huanghuai sponge area is generally high, the effect of increasing fertilizer production is declining, and the application of organic fertilizer is insufficient, and the deficiency of trace elements such as boron and zinc occurs, and the problem of high-yield cotton should be mastered. From the beginning of the bud to the first fertilizer, the main reason for chasing the second fat in the flowering and belling period. In the principle of distribution of base fertilizer and top dressing, 20% to 45% of nitrogen fertilizer is used for top dressing; potassium fertilizer based top dressing (initial flowering stage) is half. For the weaker cotton field, combined with application of mixed spray 0.5% ~ 1.0% urea and 0.3% ~ 0.5% potassium dihydrogen phosphate solution 50 ~ 75 kg / time, spray every 7 to 10 days, continuous spraying 2 ~ 3 times.
35%~50% of cotton nitrogen fertilizer in the middle and lower reaches of the Yangtze River is used as top dressing; for weak cotton fields, 0.5%~1.0% urea and 0.3%~0.5% potassium dihydrogen phosphate solution 50~75 kg/time, Spray once every 7~10 days and spray continuously for 2~3 times.
The method of topdressing application of film cotton in Xinjiang cotton area is mainly characterized by integrated regulation of water and fertilizer.
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