Discussion on Comprehensive Prevention of Cotton premature Senescence from cultivation

Cotton premature senescence refers to the phenomenon that cotton leaves wither and yellow in advance under suitable climatic conditions. in the field, it shows that the leaves lose green and yellowing between the leaves after the full flowering stage, and the etiolated leaves start from the farthest away from the main stem, from top to bottom, and develop from outside to in. the leaves gradually withered and fell off. Premature senescence has a great impact on the yield and quality of cotton. The earlier it occurs, the greater the impact. Generally, the yield can be reduced by 10% to 40%.

The premature senescence of cotton is because the fertilizer and water needs of normal growth of cotton can not be met, which leads to premature senility and early defoliation, which is shown as follows: first, it is difficult to meet the needs of cotton growth due to insufficient or uneven fertilization in cotton field; second, the root absorption capacity is weak due to poor root development or poor environment in the middle and later stage, and the nutrients absorbed by roots can not meet the needs of normal cotton growth. Third, Verticillium wilt affects the transport capacity of vascular bundles, so that the water and inorganic nutrients absorbed by roots can not be transported to stems and leaves and other organs in time. Therefore, premature senescence of cotton can be classified as a physiological disease, which is often caused by the interaction of many causes, which is easy to prevent and difficult to treat.

In view of the above causes of premature senescence of cotton, it can be seen that to prevent premature senescence, we should first apply sufficient fertilizer, then cultivate strong seedlings, protect roots, and finally control diseases in time. In terms of cultivation techniques, the author summarizes the following nine comprehensive control measures to discuss with you:

1. The most effective rotation of crop rotation can not only avoid the shortage of trace elements in cotton field caused by continuous cropping for many years, but also effectively reduce the occurrence and harm of soil-borne diseases, especially Fusarium wilt and Verticillium wilt. Cotton rotation with @ # @ 245 crop rotation is recommended in central and southern Hebei.

Second, adequate moisture cultivation is very important for cotton not to rush to sow in soil moisture, because this often requires watering after emergence, which causes low temperature and high humidity in the cotton field, which is very easy to break out in the seedling stage, which is disadvantageous to the cultivation of strong seedlings.

Third, the application of fertilizer should be reasonable. The three main elements of nitrogen, phosphorus and potassium should not only be fully applied, but also balanced. The fertilizer requirement rule of cotton is about 3 ∶ 1 ∶ 3, so the mu usage of pure nitrogen, phosphorus and potassium is not less than 12 kg, 4 kg and 12 kg respectively without taking into account soil available nutrients. In the application of the main elements, appropriate supplement of a certain amount of micro-fertilizer, such as 2 kg of borax per mu and 1 kg of zinc sulfate as base fertilizer. Paying attention to foliar fertilizer spraying in the middle and later stage of cotton can also effectively prevent premature senility.

4. the suitable sowing time for strong seedlings is early, it is easy to be affected by cold current or low temperature before emergence, and the disease is easily affected by low temperature after emergence. The suitable sowing date of plastic film cotton in central and southern Hebei is after April 20, and it is best not to sow before this time.

Fifth, plucking hoe in bud stage can not only reduce the harm of weeds, but also effectively increase soil temperature and cultivate strong seedlings, especially in seedling stage and bud stage.

Sixth, the first pruning slightly delayed the development of cotton roots at seedling stage than aboveground parts, and retaining as many green parts as possible to synthesize nutrients can promote root development, so it is suggested that the time of first pruning and branching should be postponed until after budding. And do not "stroke the trouser leg" during pruning.

7. the main purpose of plastic film mulching in cotton field is to increase soil temperature and reduce water evaporation. Plastic film is very effective before bud stage, but after mid-late June, because the air temperature has already risen and the rainy season has come, plastic film has lost its effect at this time, and even in the case of high temperature and humidity, it is easy to lead to the decline of root absorption capacity in advance, so we should uncover the film in time, no later than the end of June.

Eighth, pest control should be timely in seedling disease, verticillium wilt, late leaf spot disease, aphids and red spiders, which can promote the occurrence of premature senility of cotton, and should be prevented in time. Carbendazim, chlorothalonil, etc., and imidacloprid, triclofenac, etc. can also be added when spraying medicine. It has a certain preventive effect on this kind of diseases and insect pests.

9. Drought in the early stage of drought, waterlogging and drainage affected the development of root system; in the middle and later stage, stagnant water in cotton field promoted root death, and stagnant water in the field should be discharged in time due to watering.