Detailed Explanation of Key Points for Cotton Water Floating Seedling Technology

1. Seedbed preparation: Each seedbed (per mu) requires excavating a site 1.1-1.2 m wide, 20 cm deep, and 2.2 m long, with a flat bottom and compacted surroundings.

2. Film laying: Select a 0.06-0.1 mm thick film and lay it on the excavated seedbed, pressing it tightly against all sides of the seedbed, and check for leaks and air bubbles.

3. Substrate tray filling: Spray water on the substrate until it forms a ball when squeezed by hand, without water dripping between fingers, and it naturally breaks apart when dropped, then fill it into the seedling tray, shaking the substrate until it is 1-1.5 cm below the tray surface.

4. Nutrient solution preparation: First mix each bag of special fertilizer with 5 kg of water to make a mother solution, stir well, pour it into the seedling pool, then quickly add enough clean water to reach 150-200 kg, and mix into a uniform nutrient solution.

5. Sowing: Sow the treated seeds when the water temperature is stable above 17°C. For sprouted seeds (sprout length must not exceed one cottonseed length), sow 1 seed per hole in the center of the tray cell, with the sprout tip facing down.

6. Covering: Cover with substrate to 1-1.5 cm, level with the tray surface.

7. Tray placement and disinfection: Place the trays into the pool solution and immediately use a sprayer to spray fungicides such as carbendazim on the tray surface for disinfection.

8. Management before sprouting: Generally, on sunny days, only cover with a plastic low tunnel in the morning and evening; on rainy days, the film must be covered, but both ends of the tunnel should be left open, with ventilation openings around the sides, so that there is no mist or water droplets inside the film.

9. Management after sprouting: After seedlings emerge uniformly, do not cover with film day or night when it is not raining; on rainy days, cover the top and ventilate the sides. When dense flow occurs, promptly cover with film to keep warm or move the trays indoors to prevent cold damage. On sunny days, remove the film entirely to avoid high-temperature damage to seedlings.

10. Seedling hardening and digging: After two true leaves appear, the root system can be separated from the nutrient solution for 1-2 hours of intermittent hardening. According to growth conditions, spray mepiquat chloride or chlormequat (1 g each time) as appropriate to prevent leggy seedlings. Also promptly control pests and diseases.

11. Timely transplanting: The suitable transplanting period is from 1 leaf heart to 3 leaf hearts. For hybrid F1, the row spacing is 1-1.2 m and the plant spacing is 50-60 cm. When transplanting, do it on fully overcast days or after 4 PM on sunny days when the soil is moist, and water after transplanting to help the plants establish.