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First, the reasons for lack of seedlings 1. Seed internal factors (1) low seed vigor During the seed development, the mother plant is affected by environmental conditions, the maturity is reduced, resulting in reduced seed vigor; after harvest, the seeds contain water or high humidity, causing seed vigor Falling, sowing without germination test, resulting in field lack of seedlings. (2) Seed germination potential and germination rate are low Seed germination potential is low. The seed germination and emergence are not rapid, the uniformity is poor, and the activity is low. The germination rate is low and the seedling emergence rate is low after sowing, which may easily lead to lack of seedlings in the field. 2. Seed external factors (1) Soil moisture is too high or too low Soil moisture in sowing or excessive rain after sowing in case of excessive moisture, respiratory metabolism is slow, affect the emergence, humidity is too long, there are bad species. Poor soil moisture, lack of moisture, can not meet the minimum water requirement of the seed germination, causing the seed not to germinate. (2) Low soil temperature Because of continuous low-temperature weather after sowing or sowing, the activity of seed enzymes is reduced, the respiration is weakened, and the germination is delayed. If the humidity is high, the seedlings are easily rotted. (3) Insufficient sowing of soil oxygen, excessive soil moisture or excessive compaction, poor soil permeability, and insufficient oxygen to affect germination, resulting in lack of seedlings. (4) Poor site preparation quality Because the site preparation quality did not reach the six-character standard of “slug, flat, pine, crushed, net, and homogeneousâ€, the soil block was large, the alkali-packed was more, and the residual film and residual weeds were more, affecting emergence. (5) Poor seeding quality When planting, the membrane is uneven, the soil is loose, and it is easy to be blown by strong winds. The seeds are sown in depth. Some seeds are sown on the surface to form floating seeds, which is not conducive to emergence; Poor seed, high porosity, broken bars. (6) The seedlings are not timely applied in the cotton field under the film-on-demand cultivation mode. The seedlings are not released in time. In case of high temperature, they will burn or burn the dead seedlings. In case of low temperature, the seedlings will be damaged due to frostbite. (7) Planting methods Since cotton blight, anthracnose, and red rot may be overwintering in the soil with the residue, sowing before planting can cause rotten seed, rotten buds, so continuous cropping is generally lower than the rotation of cotton. Second, preventive measures 1. Strict seed quality Seed purity of not less than 95%, a degree of purity of not less than 99%, germination rate of not less than 80%, water content of not more than 12%. After the seeds are coated, they are aired for broadcast. 2. Land preparation For the land with flat topography and medium fertility, conduct soil testing and formula fertilization, plunge about 25 centimeters deep, plant the land before planting, and use maggots as the center, to achieve the word “墒, æ¾, 碎, å¹³, 净, é½â€. standard. 3. Control of pests and diseases For the prevention and control of cotton seedling blight, anthrax, red rot caused by rotten species, rotten buds, for the seeds without a coating to use seed dressing. Available in 0.5% of the seed amount of 50% of carbendazim wp, 30% of mycobacterial enemies wp or 50% of the seed amount of 0.6% thiophanate-methyl wp and account for 0.8% of the seed content of 75% of 3911 or 40 % Methylisothionate mixed dressing, 2 to 3 kg of water per 100 kg of seed. 4 timely sowing when the soil temperature of 5 cm soil stable above 14 °C can be sown. According to the meteorological department's forecast, under the condition of no low temperature and cold damage, early sowing can be appropriately performed to fully utilize the effect of temperature increase of the plastic film. 5. Improve the quality of sowing on the basis of fine soil preparation. Strict sowing quality, so that the next seed uniform, accurate access, tight soil, membrane surface flat, membrane edge, plug straight end, sowing depth of 2 to 3 cm, on demand The porosity does not exceed 2%. 6. Timely release of seedlings The cotton field under the film-on-demand cultivation mode was used to put seedlings and seal soil in a timely manner to prevent cotton seedlings from being exposed to membranes, and burns were killed or frozen. The seedlings were treated with the on-demand film-on-demand cultivation method. The soil in Yuchunyu hole was easy to compact and emerged. Difficulties should be promptly broken to help seedlings unearthed. 7. Replanting in time After sowing, in case of continuous rain, cold damage, etc., should be timely seedling reseeding, or soaking seed replanting. 8. Rotation of crop rotation is best done with rotation of grass crops to improve soil structure, reduce occurrence of cotton seedling diseases, and increase seedling emergence rate.