To grow strong cotton seedlings, the seedbed must be protected against five major threats
Common problems in cotton nutrient-cup seedbeds are mainly manifested as drought, waterlogging, disease, fertilizer burn, herbicide damage, and cold damage to seedlings, heat injury to seedlings, and spindly seedlings. The preventive measures are as follows: The moisture content of the cup soil should be moderate. The nutrient-cup seedbed should be located where both drainage and irrigation are convenient. The ideal moisture content of the cup soil is such that it forms a ball when squeezed by hand and breaks apart when dropped to the ground. ...
Common problems in cotton nutrient-cup seedbeds are mainly manifested as drought, waterlogging, disease, fertilizer burn, herbicide damage, and cold damage to seedlings, heat injury to seedlings, and spindly seedlings. The preventive measures are as follows:
The moisture content of the cup soil should be moderate. The nutrient-cup seedbed should be located where both drainage and irrigation are convenient. The ideal moisture content of the cup soil is such that it forms a ball when squeezed by hand and breaks apart when dropped to the ground. After sowing cotton and covering with soil, water thoroughly in one application, watering until it slowly permeates downward. After covering with film, ensure sufficient soil moisture; do not uncover the film at will, and do not uncover it until the seedlings emerge uniformly. Around the seedbed, surface water should be drained and seepage water filtered out, so that the ditches are dry after rain.
Guard against disease at three points. First, both the nutrient-cup soil in the seedbed and the fine soil covering the cups after sowing must be disinfected with chemicals to prevent pathogens in the soil from harming the cotton seedlings. Second, except for refined cottonseed that has already been disinfected, seed sown as fuzzy seed or delinted seed must be treated with a chemical seed dressing for sterilization. For both soil and cottonseed disinfection, chemicals such as carbendazim and thiophanate-methyl can be used. Third, after the cotton seedlings emerge uniformly, spray Bordeaux mixture and similar chemicals to prevent pathogen infection, but the dosage should not be too high, and repeated spraying must be avoided to prevent chemical injury.
Regulate temperature and control humidity to strive for early seedlings. Covering with plastic film is intended to increase accumulated temperature and promote early emergence and early growth of cotton seedlings. Regulating temperature and controlling humidity is the means of scientifically applying temperature and light conditions. After the cotton seedlings emerge uniformly, when the air temperature steadily passes 12°C, the two ends of the seedbed can first be uncovered for ventilation and dehumidification to harden the seedlings, then gradually uncovered further to prevent spindly excessive growth. When the air temperature steadily passes 16°C, the film can be uncovered in the morning and covered again at night. To prevent sudden cold waves and freezing injury, do not transplant the cups and do not remove the film from the bed. When the atmospheric temperature reaches above 20°C, to prevent heat injury to seedlings, open the film day and night and water to adjust soil moisture. At the same time, advocate raising seedlings in large cups, keeping cups in place to restrain seedling growth, eliminating weak seedlings, controlling excessive growth and promoting vigor, and striving for early growth while maintaining stability.
Topdress according to seedling condition to grow strong seedlings. After the cotton seedlings emerge uniformly, those growing well need only one topdressing as send-off fertilizer before transplanting, while those with insufficient base fertilizer need two topdressings. The first should mainly be clear water and manure; the second can be a 0.5% to 1.0% urea solution to promote the small and catch up the large, so that strong seedlings leave the bed. But the fertilizer concentration each time should not be too high; dilute, quick-acting, and fast is best.