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 a porous polyethylene foam seedling tray as the carrier, with a mixed substrate as support, and places the seedling tray carrying cotton seeds into a nutrient solution water bed for cultivation. It has notable effects in saving seeds, saving labor, increasing yield, and improving efficiency. Compared with conventional nutrient bowl seedling raising and transplanting of cotton, it saves more than 40% of seed quantity, and reduces labor by about 10 workdays per mu for seedling raising and transplanting. The cotton seedlings have well-developed root systems, a low degree of lignification, and are soft and elastic, not easily broken, with strong vitality and uniform growth. During the process of taking out seedlings for transplanting, there is little root damage and a short recovery period, and the yield increase is 7-10% compared with nutrient bowl seedling raising and transplanting. This technology can be applied on a factory-scale basis, and is also suitable for farmers to plant in the vacant flat ground 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 vacant flat ground in front of and behind houses that is sheltered from the wind, faces the sun, is convenient to manage, and is 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 0.006-0.01 mm thick film on the bottom and around the seedbed so that the back of the film fits closely against the soil, with the film extending to cover 15 cm on all sides 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 testing with water, compact it with soil.

III. Filling the tray with substrate. Select a high-efficiency mixed substrate. After pouring out the substrate, moisten it evenly with water so that the substrate moisture content reaches 60% of its own weight (it forms a ball when squeezed by hand, no water flows out between the fingers, and it naturally breaks apart after being dropped). Pour the substrate evenly into the seedling tray, and scrape the surface of the seedling tray level with a hand or a bamboo or wooden strip. Shake the seedling tray so that the substrate becomes firm and drops 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. In 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, and then pour it into the seedling pool. Then rinse the bucket or basin repeatedly 2-3 times with clean water, and pour the rinse 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, for 5-6 hours each day, for 3-4 consecutive days. Seed soaking can adopt two methods: soaking with warm boiled water and soaking with warm water. For 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. For 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 with no damage and no insect holes for sprouting. Drain the selected seeds, pack them in small plastic bags, with no more than 500 g per bag. After filling, tie the bag mouths tightly, cover or wrap them with insulating materials such as rice straw, cotton clothing, or cotton quilts, and keep them warm for sprouting (sprouting temperature about 30°C). Sow when the cotton seeds break through the shell or the sprout grows to half the length of a cotton seed. Sow 1 seed per hole, in the center of the hole, with the sprout tip facing down, so that the sprout tip points exactly to the small hole at the bottom of the hole. The sowing depth should preferably be 1-1.5 cm. Gently press the seed down with a finger, and be careful never to break the root tip. After sowing, cover with substrate 1-1.5 cm thick, with the substrate level with the surface of the seedling holes as the standard.

VI. Seedbed management. Immediately after sowing, place the seedling tray into the seedbed. It may also be placed indoors first, and then placed into the seedbed after the seedlings emerge uniformly. 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 arch tunnel for seedling raising. Cotton water-floating seedling raising adopts sprouted sowing, so seedbed management is fundamentally different from nutrient bowl seedling raising. In this seedling raising method, special attention must be paid to high-temperature damage to sprouts. Before seedling emergence, if it is generally not raining, when the temperature is above 20°C, cover only in the early morning and evening, with the covering time from 6:30 p.m. to 7:30 a.m. On rainy days, the film must be covered, but both ends of the arch tunnel should be opened, and then ventilation openings should be made around the arch tunnel. The ventilation effect should reach the point where there is no mist and no water droplets inside the film. After the cotton seedlings emerge completely, on days when it is not raining, when the daily minimum temperature is above 18°C, the film may be left uncovered day and night, with the top covered on rainy days and ventilation 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 completely uncovered to harden the seedlings. After the cotton seedlings have 2 true leaves, on sunny days the seedling trays can be raised so that the root systems leave the nutrient solution, for intermittent 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. In addition, timely control of diseases and insect pests is also needed.

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 1200 plants per mu, with row spacing of 1 m and 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 tray, lift it up, hold the base of the cotton seedling stem with your 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 seedling hoe or small shovel to transplant directly, making the root system spread out and the young seedling stand upright. After transplanting, promptly water with settling water and survival water.