Experimental Demonstration and Application of Factory-Based Soilless Seedling Raising of Cotton in the Dongtai Area
Factory-based soilless seedling raising of cotton is a seedling revolution in the history of cotton cultivation. It breaks the decades-old cultivation system of raising seedlings in nutrient pots and transplanting them, making cotton seedling raising and transplanting a simple, rapid, time-saving, labor-saving and cost-saving cultivation method, and opening up a new path for cotton cultivation. In 2003, Dongtai City introduced factory-based soilless seedling raising and transplanting trials. In 2004 and 2005, this technology was introduced successively in Tangyang and Luegang for soilless seedling raising and large-area transplanting trials and demonstrations. The details are summarized as follows.
1 Basic information on the trials and demonstrations
In 2003, Xinhong Village, Tangyang Town, in our city introduced soilless-raised cotton seedlings from Henan and carried out trial planting on 1 mu of land. In 2004, the Tangyang Cotton Ginning Mill introduced this technology for seedling raising, and the demonstration area that year was about 4000 mu. In 2005, Nanjing Red Sun Group cooperated with our city's Chunhua Seed Industry to continue the development of the factory-based soilless cotton seedling raising project in Yushe Village, Luegang Town. The demonstration area that year was 1500 mu, mainly concentrated in Luegang Town.
2 Trial and demonstration results
2.1 Yield situation In 2003, due to low temperature and continuous rain in the early stage, cotton developed late in the later stage, and the lint yield per unit area was about 55 kg, with the large-area yield slightly reduced. In 2004, for factory-based soilless cotton seedling raising and transplanting: Luegang Town increased yield by 12.8% compared with the large area; Haifeng Town decreased by 6.3% compared with the large area; Lianyi Town's total bolls per mu decreased by 10.8% compared with the control; Cao/ Town decreased by 10.7% compared with the control; Tangyang Town decreased by nearly 10% compared with the large area. In 2005, the lint yield per unit area of cotton cultivated by soilless seedling raising in Luegang Town was 75.6 kg, an increase of 10.4 kg over pot-raised cotton (not in the same field), or 16%; in Tainan Town, the total bolls per mu for soilless seedling raising were 53,000, and the lint yield per unit area was 97 kg; in Liangduo Town, the total bolls per mu were 36,900, 7,700 fewer than the control, a decrease of 17.3%; in Cao/ Town, the total bolls per mu were 55,500, 1,700 fewer than the large area, a decrease of 3%; in Sancang Town, the lint yield per unit area was 65.1 kg, 6.7 kg less than the large area, a decrease of 9.3%; in Haifeng Town, the lint yield per unit area was 51.5 kg, 11.65 kg less than the large area, a decrease of 18.4%; in Touzao Town, the total bolls per mu were 44,700, 3,300 fewer than the large area, a decrease of 6.8%.
2.2 Transplanting survival situation Generally, for soilless seedling raising and transplanting, as long as the soil is pressed firm and earthed up during transplanting, the survival rate is above 90%, and in good fields it can reach 100%; otherwise it is only about 80%. Under normal conditions, live-plant water should be applied twice. According to a survey in Luegang Town, as long as the roots and soil are firmed after planting, sensitivity to watering is not strong. In this town in 2004, during the transplanting period the soil moisture was good and there was a lot of rain, and after watering the cotton seedling death rate exceeded 20%, while the death rate of seedlings not watered was only about 8%. In 2005, the survival rates of both watered and unwatered seedlings reached 95%, with no obvious difference. They believed that under conditions of sufficient soil moisture, the concentration of the "rooting agent" adhering to the cotton seedling roots after watering was diluted and weakened by the water, so the effect was poor and seedling death was severe.
2.3 Growth and development characteristics Soilless-raised and transplanted cotton seedlings show a long live-planting and seedling-recovery period after transplanting, slow growth at the seedling stage, accelerated growth and development after squaring, and a large proportion of autumn bolls and late autumn bolls. Generally, for soilless-raised and transplanted cotton seedlings, the seedling-recovery period is 15-20 days before new leaves emerge. In a 2005 trial in Cao Town, transplanting was on May 11, and new leaves began to grow on May 28, with a seedling-recovery period of 17 days, while in 2004 the seedling-recovery period was even longer, nearly 1 month. In this town, an investigation on July 20 found that soilless-raised and transplanted cotton seedlings were 11 cm shorter in plant height, had 2 fewer true leaves, 2.6 fewer fruit branches and 12.2 fewer fruit nodes than nutrient-pot-raised and transplanted cotton seedlings. In an investigation on August 15, plant height was only 2.3 cm shorter, fruit branches only 1.4 fewer, and fruit nodes only 3.2 fewer. The growth and development process was obviously accelerated. In an investigation on September 10, plant height was only 1.5 cm shorter, fruit branches 0.9 fewer, and fruit nodes only 1.7 fewer, basically comparable to nutrient-pot-raised and transplanted cotton seedlings. According to systematic investigation in Haifeng Town in 2005, the proportion of autumn bolls of soilless-raised and transplanted cotton seedlings was 41.4%, 22.5 percentage points higher than large-area nutrient-pot-raised and transplanted cotton seedlings, and the proportion of late autumn bolls was 30.5%, 28.4 percentage points higher than large-area nutrient-pot-raised and transplanted cotton seedlings.
2.4 Disaster resistance situation Because factory-based soilless-raised cotton grows faster in the middle and late stages and has a large proportion of autumn bolls and late autumn bolls, it has strong disaster-compensation ability in the later stage and does not senescence early. However, because soilless-raised and transplanted cotton has shallow roots, its wind resistance and lodging resistance are not strong, so in the middle and late stages high ridges should be added. At the same time, because soilless-raised and transplanted cotton develops late, there is a risk of excessive vegetative growth and late maturity in the later stage; in years with rapid temperature drops and early frost, this will affect cotton yield formation.
3 Risk assessment
3.1 Advantages Cotton soilless seedling raising has the advantages of large-scale production, labor saving and cost saving, and is especially suitable for larger-area contractors and farm production. It not only saves labor and cost, but also saves land for pot beds and alleviates the contradiction of labor shortage. A 2004 survey in Tangyang Town found that cotton transplanting saved about 20 yuan per mu in cost compared with nutrient-pot seedling raising and transplanting; a 2005 survey in Luegang Town found that soilless cotton seedling raising and transplanting could save 79 yuan per mu in cost compared with nutrient-pot seedling raising and transplanting, and save about 0.1 mu of cultivated land.
3.2 Weaknesses First, the yield is lower than that of nutrient-pot-raised and transplanted cotton, generally reduced by about 10%. Second, it develops late, with a large proportion of autumn bolls and late autumn bolls, and in years with rapid temperature drops and early frost the yield reduction may be even greater. Third, the root system is shallow and lodging resistance is not strong. Fourth, seedling raising risk is relatively high; large-scale factory-based seedling raising requires every technology and every link to be in place in a timely manner, and the slightest carelessness may cause large-area seedling death or failure to emerge.
4 Related supporting cultivation practices
4.1 Selecting suitable preceding crops Compared with nutrient-pot-raised and transplanted cotton, factory-based soilless-raised and transplanted cotton develops later, so relatively early preceding crops must be selected, generally requiring blank stubble, vegetable stubble and interplanting stubble. If wheat-after transplanting stubble is selected, vacant transplanting rows should be reserved in winter for digging and turning to mature the soil, and transplanting should be rushed immediately after wheat harvest.
4.2 Cultivating suitable seedling age For factory-based soilless-raised and transplanted cotton, the seedling age should not be too old or too young. If too young, there are few leaves, poor roots, little vegetative mass and few photosynthates, and seedling development is even slower; if too old, the main root grows downward, the cotton seedlings become thin and stiff, the survival rate after transplanting decreases, and seedling development is relatively poor. Generally, a seedling age of about 25 days, at the two-leaf-one-heart stage, is suitable.
4.3 Applying early-promoting cultivation Factory-based soilless cotton
For transplanted cotton seedlings, because early-stage plant development is slow and growth is late, early-promoting cultivation measures must be adopted in cultivation management. First, use plastic film transplanting as much as possible, which can both preserve soil moisture and increase temperature, promoting cotton growth. Second, apply live-plant water well to promote the cotton seedlings to recover as soon as possible. Third, after recovery, appropriately apply seedling fertilizer to promote the cotton seedlings to grow as soon as possible.
4.4 Strengthening disaster-resistance management Factory-based soilless-raised and transplanted cotton has shallow roots and is prone to lodging under strong winds and heavy rain. Therefore, during transplanting it can be planted appropriately deeply; the eastern coastal cotton area can use high ridges to stabilize roots, prevent lodging and reduce waterlogging. The western Lixiahe cotton area can use small-bed equal-row transplanting, which is conducive to draining water and reducing waterlogging damage.
4.5 Proper chemical regulation Factory-based soilless-raised and transplanted cotton grows slowly in the early stage and faster in the later stage. In chemical regulation, the early stage should mainly promote growth, and the later stage should mainly control vegetative growth. In the selection of chemicals, regulators with both promoting and controlling effects should be chosen. For example, choose "Lingfengbao" at about 20 ml per mu at the bud stage, 30-40 ml at the early flowering stage, and about 60 ml at the full flowering stage; after cotton topping, 7-10 days later, use "Lingfengbao" at 80-120 ml per mu for chemical topping to promote reproductive growth; 15-20 days before the first frost, use ethephon for ripening.