How to prevent cotton bud and boll shedding from growing cotton

(1) the general law of bud and boll shedding

The ratio of ① bud and boll shedding in bud and boll shedding, the general trend of the ratio of bud shedding to boll shedding is that the boll shedding rate is higher than the bud shedding rate, and the proportion is about 3:2.

The buds and bolls of ② shed most at the age of budding after ll~20, while the big buds fell off less at more than 20 days. The young bolls at 3-8 days after flowering were the most easy to fall off, and the young bolls at 3-5 days were the most, while those more than 10 days were rarely shed.

The parts of ③ bud and boll shedding are generally less in the lower fruit branch and more in the upper fruit branch, less in the bud and boll near the main stem and more in the far away from the main stem. However, when the density is too high, there is too much fertilizer and water, and when the cotton plant grows excessively, the position of bud and boll shedding is opposite to that mentioned above.

During the period of ④ bud and boll shedding, cotton rarely fell off before the early flowering stage, then gradually increased, reached the peak at the peak of flowering and boll setting, and then gradually decreased. According to the study, the number of shedding in the peak period of flowering and bolling from late July to early August accounts for about 56% of the total number of shedding.

Differences of bud and boll shedding among different cotton species and varieties in ⑤. According to statistics, the shedding rate of upland cotton is the highest, followed by China cotton, and sea island cotton is the lowest. There is a great difference in bud and boll shedding rate among upland cotton varieties, which is as high as 35%.

(2) the reasons for the falling off of buds and bolls

① physiologically exfoliated. Physiological shedding is the basic cause of bud and boll shedding, accounting for about 70% of the total shedding rate. There are many factors causing physiological shedding, which mainly include the following points: first, the lack of organic nutrients or improper distribution. When the external environmental conditions are not suitable, the cotton plant grows thin or overgrown, resulting in insufficient or improper distribution of organic nutrients in the cotton plant, so that the bud and boll can not get sufficient organic nutrients and fall off. In the external environmental conditions, fertilizer, water, light, temperature and other factors have the greatest impact on physiological shedding. Second, there is no fertilization. Unfertilized young bolls inevitably lead to shedding because of their weak growth and metabolism and poor ability to absorb nutrients. There are many reasons affecting fertilization, such as rainfall, high temperature, drought and other adverse environmental conditions during flowering, which will destroy pollen and pollination and fertilization process. The third is the imbalance of plant hormones. Cotton plant contains five kinds of endogenous hormones: auxin, gibberellin, mitotic cord, abscisic acid and ethylene. When the content of these hormones is changed, the balance between hormones will be lost and the bolls will fall off.

② diseases and insect pests. Diseases and insect pests can cause bud and boll shedding directly or indirectly, such as Miridae, cotton bollworm, cotton aphid, etc., and the main diseases are Fusarium wilt, Verticillium wilt and red leaf stem blight.

③ mechanical damage. During the growing period of cotton, careless field operation and management, or attacked by hail or storm, will damage branches and leaves or buds and bolls, causing buds and bolls to fall off.

(3) main measures to prevent bud and boll from falling off

① improved the condition of fertilizer and water. Mainly for barren cotton fields, this kind of cotton fields have insufficient supply of fertilizer and water, and cotton plants are easy to senescence prematurely in the later stage. Watering and topdressing had significant effects on reducing bud and boll shedding.

② regulates the relationship between vegetative growth and reproductive growth. Mainly aimed at cotton fields with good soil fertility, this kind of cotton fields are prone to overgrowth. Comprehensive cultivation measures such as fertilizer and water, mid-tillage, pruning and the use of growth regulators should be adopted to coordinate the relationship between vegetative growth and reproductive growth, so as to make the distribution of organic nutrients reasonable and reduce the shedding of buds and bolls.

③ used reasonable close planting to improve the light condition of cotton field. The shedding of buds and bolls can be reduced by establishing a reasonable population structure, reducing shading, improving field lighting conditions and improving light energy utilization efficiency.

④ strengthens the integrated control of diseases and insect pests. Reduce the shedding of buds and bolls caused by diseases and insect pests to a minimum.