Detailed Explanation of the Key Points of Cotton Water-Floating Seedling Raising Technology

"Cotton water-floating seedling raising technology" is a new cotton planting technology developed by agricultural experts in Hunan Province. This technology uses porous polyethylene foam seedling trays as the carrier, with a mixed substrate as support, and places the seedling trays carrying cotton seeds into a nutrient solution water seedbed for cultivation. It has significant effects in saving seeds, saving labor, increasing yield, and improving efficiency. Compared with conventional nutrient bowl seedling transplanting cotton, it saves more than 40% of seed usage, and reduces labor by about 10 person-days per mu for seedling raising and transplanting. The cotton seedlings have well-developed root systems, a low degree of lignification, are soft and elastic, not easy to break, have strong vitality, and grow neatly and uniformly. During the process of taking seedlings for transplanting, there is little root damage, and the seedling recovery period is short. Compared with nutrient bowl seedling transplanting, it increases yield by 7-10%. This technology can be applied on a factory-scale basis, and is also suitable for farmers to plant in the open spaces in front of and behind their houses. In case of disastrous weather, the seedling trays can be quickly moved indoors to avoid seedling-raising risks. "Cotton water-floating seedling raising technology" has been appraised by experts as reaching the international advanced level. It is a major technological revolution in cotton production and has great value for promotion and application. Its operating procedures are introduced as follows.

I. Seedbed preparation. Choose cultivated land or open spaces in front of and behind houses that are sheltered from the wind and face the sun, convenient for management, and close to the cotton field. The seedbed should be 1.1-1.2 m wide, 20 cm deep, and 2.1 m long. Dig the seedbed with a hoe and tamp the surroundings firmly. The bottom of the bed should be level, and stones, hard pointed plant roots and stems, etc. should be picked out.

II. Laying film in the seedbed. First wet the surroundings and bottom layer of the seedbed with water, then lay film with a thickness of 0.006-0.01 mm on the bottom and around the seedbed, so that the back side of the film fits tightly against the soil, and extend the film to cover 15 cm on each side of the seedbed. After laying the film, immediately test with water to check whether there is leakage and whether there are air bubbles under the film. If there is leakage, replace the film; if air bubbles are found, lay the film again. After the water test, compact it with soil.

III. Filling the trays with substrate. Select high-efficiency mixed substrate, pour out the substrate and moisten it evenly with water so that the water content of the substrate reaches 60% of its own weight (when squeezed by hand it forms a ball, no water flows out between the fingers, and it naturally breaks apart after falling). Pour the substrate evenly into the seedling trays, and scrape the surface of the seedling trays level with a hand or bamboo or wooden strip. Shake the seedling trays to make the substrate compact and settle to 1-1.5 cm below the tray surface, which is convenient for sowing.

IV. Preparing the seedling nutrient solution. First prepare the mother solution. Using a bucket or basin or other container, add about 5 kg of water per bag of special seedling fertilizer, stir with a hand or stick so that the fertilizer is fully dissolved, then pour it into the seedling pool. Then rinse the bucket or basin repeatedly with clean water 2-3 times, and pour the rinsing water into the seedling pool as well. After pouring the mother solution into the seedling pool, quickly add enough clean water so that each pack of fertilizer is made into 150-200 kg of nutrient solution. Stir while adding water so that the fertilizer is distributed evenly.

V. Sowing. In the Yangtze River Basin, sowing is generally carried out from April 20 to May 5. Sun the seeds 15 days before sowing, 5-6 hours per day, for 3-4 consecutive days. Seed soaking can adopt two methods: soaking with warm boiled water and soaking with warm water. When soaking with warm boiled water, soak the sunned seeds in 75-80°C warm boiled water for 2 minutes, then immediately cool them with cold water to about 45°C, and let them soak for 3-4 hours so that the cotton seeds fully absorb water. When soaking with warm water, soak the seeds in 30°C warm water for 8-10 hours, and the cotton seeds can fully absorb enough water. After soaking, remove the immature seeds floating on the water surface, take the sunken plump seeds, and select healthy seeds without damage or insect holes for germination. Drain the selected seeds, pack them separately in small plastic bags, with no more than 500 g per bag. After filling, tie the bag mouths tightly, cover or wrap with insulation materials such as rice straw, cotton clothing, or cotton quilts, and keep warm for germination (germination temperature about 30°C). Sow when the cotton seeds have cracked open or the sprout is half the length of a cotton seed. Sow 1 seed per hole, in the center of the hole, with the sprout tip facing downward, so that the sprout tip directly faces the small hole at the bottom of the hole. The sowing depth should preferably be 1-1.5 cm. Gently press the seeds down with a finger, and be careful absolutely not to break the root tip. After sowing, cover with substrate to a thickness of 1-1.5 cm, with the substrate level with the surface of the seedling holes as the standard.

VI. Seedbed management. Immediately after sowing, place the seedling trays into the seedbed. They may also be placed indoors first, and after the seedlings emerge uniformly, placed into the seedbed. When placing the trays, arrange 2 horizontally and 1 vertically. Immediately after placing the trays, spray fungicides such as carbendazim on the tray surface with a sprayer for disinfection. Then cover with film, using a small plastic-film arched shed for seedling raising. Cotton water-floating seedling raising uses germinated seeds for sowing, so seedbed management is fundamentally different from nutrient bowl seedling raising. This seedling raising method must pay special attention to high-temperature damage to sprouts. Before emergence, generally do not cover on rainy days. When the temperature is above 20°C, cover only in the morning and evening, with covering time from 6:30 p.m. to 7:30 a.m. On rainy days, film must be covered, but both ends of the arched shed should be opened, and then ventilation openings should be made around the arched shed. The ventilation effect should reach the point where there is no fog or water droplets inside the film. After the cotton seedlings emerge completely, on days without rain, when the daily minimum temperature is above 18°C, the film may be left off day and night; on rainy days, cover the top and ventilate around the sides. If a cold wave strikes, cover with film to keep warm, or move the seedling trays indoors. On sunny days, completely uncover the film to avoid high-temperature damage to seedlings. When the daily average temperature is above 20°C, the film can be fully uncovered to harden the seedlings. After the cotton seedlings have 2 true leaves, take advantage of sunny days to raise the seedling trays so that the root systems leave the nutrient solution, and carry out intermittent seedling hardening for 1-2 hours. In addition, according to the growth of the cotton seedlings, spray mepiquat chloride or chlormequat as appropriate for regulation to prevent legginess, and also promptly control pests and diseases.

VII. Transplanting of water-raised seedlings. The best transplanting seedling age is from 2 leaves and 1 heart to 3 leaves and 1 heart. Plant about 1,200 plants per mu, with a row spacing of 1 m and a plant spacing of 45-55 cm. It is best to choose cloudy days or light rainy days; on sunny days, transplant in the morning or after 4 p.m. When transplanting, take out the seedling trays, hold them up, grasp the base of the cotton seedling stem with the hand, and gently pull upward without damaging the root system, keeping the root system intact. When transplanting, there is no need to open furrows or dig holes. Use a small transplanting hoe or small shovel to transplant directly, so that the root system spreads out and the young seedling stands upright. After transplanting, promptly water with root-setting water and survival water.