Dry-wet alternating flue-cured tobacco seedling raising method suitable for northeast region

Abstract

The invention belongs to the technical field of flue-cured tobacco seedling raising, and particularly relates to a dry-wet alternating flue-cured tobacco seedling raising method suitable for northeast regions. Selecting a leeward and sunny place as a seedling raising field, building an overwintering warm shed as a seedling raising shed, and arranging a reservoir in the seedling raising shed so as to improve the temperature of water for seedling raising; a plurality of nursery ponds are manufactured in the nursery shed, the bottoms of the nursery ponds are flat, and the nursery ponds are filled with nursery water in the reservoir; putting the seedling raising tray filled with the flue-cured tobacco seeds into a seedling raising pond; the seedling raising greenhouse is ventilated every day, and in the seedling raising process, the seedling raising pond is subjected to multiple times of treatment 1 and then subjected to multiple times of treatment 2 till 7-10 days before transplanting; disease-resistant treatment is conducted, topdressing is conducted three times in the seedling raising period, seedbed fertilizer and water are cut off 7-10 days before transplanting, water control and seedling hardening are conducted, and flue-cured tobacco seedlings are transplanted into a field for planting; according to the method, a dry-wet alternating environment of the seedling bed is created, so that the effect of hardening seedlings and raising seedlings at the same time can be achieved, and moss can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of flue-cured tobacco seedling cultivation, and in particular relates to a dry-wet alternating flue-cured tobacco seedling cultivation method suitable for the Northeast region. Background Art

[0002] In the existing seedling raising method, the seedling raising pool is filled with water most of the time. Due to the cold climate in the Northeast, the long-term water storage in the seedling pool reduces the temperature at the bottom of the seedling tray, resulting in slow growth of tobacco seedlings. In addition, the long-term moisture of the seedling raising medium can easily cause the seeds to crack, affecting the germination rate. In addition, since the seedling raising pool is filled with water most of the time, it provides a more suitable living environment for moss, resulting in more moss in the seedling raising process, and the moss competes with the seedlings for water and fertilizer, which seriously affects the seed germination rate and thus affects the quality of tobacco seedlings. Summary of the invention

[0003] In view of the fact that the existing seedling raising method is not suitable for the cold climate conditions in Northeast China, the uniformity of tobacco seedlings is low, and there is a lot of moss, etc., the present invention proposes a flue-cured tobacco seedling raising method suitable for Northeast China.

[0004] In order to solve the above technical problems, the present invention provides a dry-wet alternating flue-cured tobacco seedling raising method suitable for the Northeast region, comprising the following steps:

[0005] A dry-wet alternating flue-cured tobacco seedling raising method suitable for the Northeast region comprises the following steps:

[0006] (1) Seedling preparation

[0007] Choose a location that is leeward and sunny as the nursery ground. The nursery ground should be flat, leeward and sunny, and have a low groundwater level. Build a warm shed for wintering as the nursery ground. Set up a reservoir in the nursery ground to increase the water temperature for the nursery water. Put the nursery water in the reservoir in advance.

[0008] (2) Preparation of nursery pond

[0009] Make multiple nursery pools in the nursery shed. The nursery pools are surrounded by red bricks. A nursery bed leveler is used to level the pool bottom to ensure that the pool bottom is flat. The nursery pools are filled with nursery water from the reservoir. After the nursery pools are filled with clean water, the water depth is about 1.5 cm.

[0010] (3) Seedling cultivation process

[0011] Put the seedling tray containing flue-cured tobacco seeds into the seedling pool; ventilate the seedling shed every day, first treat the seedling pool multiple times 1, and then treat it multiple times 2 during the seedling raising process until 7 to 10 days before transplanting; carry out disease resistance treatment, apply topdressing 3 times during the seedling raising period, cut off the fertilizer and water in the seedling bed 7 to 10 days before transplanting to control water and harden the seedlings, and move the flue-cured tobacco seedlings into the field for planting;

[0012] The treatment 1 is drainage-covering seedling medium-water storage treatment;

[0013] The treatment 2 is a drainage-water storage treatment.

[0014] The drainage-covering seedling medium-water storage treatment is to drain the water in the seedling pool 4 to 5 days after sowing, then cover the entire seedling tray with a layer of seedling medium, and add seedling water to the seedling pool 2 to 3 days later; the multiple treatments 1 are 3 treatments 1;

[0015] The drainage-water storage treatment is to drain the water in the nursery pond again after 4 to 5 days, and to add nursery water to the nursery pond after 2 to 3 days.

[0016] The seedling raising shed is a civil construction structure and a steel frame, and the shed film is a polyvinyl chloride drip-free film, and the shed film is covered with heat preservation and warming facilities.

[0017] A black polyethylene film is laid on the bottom of the nursery pond, and soil is used to compact and fix the film around it to ensure that the nursery pond is watertight. The nursery pond is filled with the nursery water prepared in the reservoir.

[0018] The seedling tray containing flue-cured tobacco seeds is provided with a seedling substrate in the seedling tray, sowing seeds in the seedling substrate, and after sowing, evenly sprinkling 2-4 mm of covering soil on the seedling substrate in the seedling tray;

[0019] The sowing is carried out by using a seeder with self-contained hole pressing and sowing functions, 1 to 2 coated seeds are sown in each seedling hole, 2 seeds are sown in the two long side seedling holes of the seedling tray, the sowing depth is controlled at 0.3 to 0.5 cm, and after sowing, 2 to 4 mm of covering soil is evenly sprinkled above the tray.

[0020] The seedling raising shed is ventilated from 8 to 16 o'clock every day, and the temperature in the shed is maintained at 25 to 30° C. and the humidity is 70%.

[0021] The disease resistance treatment is to spray 600 times diluted 80% mancozeb powder, 800 times diluted 80% thiophanate-methyl powder or 500 times diluted 25% carbendazim to prevent and control anthracnose, and to spray 600 times diluted 58% metalaxyl mancozeb wettable powder, 1000 times diluted 50% thiophanate-methyl wettable powder or 1000 times diluted 75% thiophanate-methyl wettable powder to prevent and control damping-off disease; use antiviral agents to prevent mosaic disease; spray once every 10 days.

[0022] The topdressing is to select diammonium phosphate as a seedling fertilizer, which is applied three times to increase the stress resistance of tobacco seedlings.

[0023] The specific steps of topdressing are: dissolving diammonium phosphate in water, and fertilizing the seedling pool while filling the seedling pool with water, the first time of fertilizing is selected between 15 and 16 days after sowing; the second time of fertilizing is between 27 and 28 days after sowing; the third time of fertilizing is between 35 and 36 days after sowing, water and fertilizer are added from the seedbed, and clean water is used to spray the tobacco seedlings after fertilizing, and the amount of topdressing is 200 grams per 10,000 seedlings.

[0024] The water control and seedling hardening is to control water and harden the seedlings step by step 7 to 10 days before transplanting, and the degree of water control is suitable for the tobacco seedlings to wilt slightly at noon and recover in the morning and evening. Open the vents under the greenhouse 5 days before transplanting to ventilate the tobacco seedlings to adapt to the external climate. Spray the inhibitory agent 1 day before transplanting to protect the tobacco seedlings.

[0025] Beneficial effects of the present invention:

[0026] Compared with the prior art, the present invention drains the water in the nursery pool after a period of water storage, thereby creating an alternating dry and wet environment for the nursery bed, so as to achieve the effect of hardening the seedlings while raising them; the dry and wet alternating nursery method is suitable for the cold climate in the northeast region because the substrate temperature is not affected by the water temperature after the nursery pool is drained. In addition, the dry and wet alternation of the nursery pool is conducive to promoting the full growth of the lateral roots of the tobacco seedlings, facilitating the control of large and small seedlings, making them meet the standard of strong seedlings, and improving the seedling rate; and after drainage, the nursery substrate is covered on the nursery bed, which further enhances the effect of the dry and wet alternation, can effectively avoid the photosynthesis of algae, and reduce the occurrence of moss. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a picture of the interior of the seedling raising shed in Example 1 before seedling raising.

[0028] Figure 2 This is a picture of the seedling raising pond after being filled with water for seedling raising in Example 1.

[0029] Figure 3 These are pictures of the seedling raising process in Example 1. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be described in further detail below.

[0031] Example 1

[0032] The technical solution of the present invention is further described below in conjunction with an embodiment. The flue-cured tobacco seedling raising method with alternating dry and wet seedling beds provided by the present invention comprises the following steps:

[0033] 1) Selection of seedling raising site: The seedling raising site should be located in a place with flat terrain, sheltered from the wind and facing the sun, with low groundwater level, clean water source (well water, tap water), fast ground temperature recovery, convenient transportation, isolation from poultry and livestock, and no tall shade objects around. Sites or greenhouses where tobacco, tomatoes and other Solanaceae, Cruciferae and Cucurbitaceae crops have been planted in recent years cannot be used as seedling raising sites.

[0034] 2) Construction of the seedling shed. The seedling shed is a warm shed for wintering. The civil structure and appearance specifications are 50 to 80 meters long, 7 to 9 meters wide, and 3 meters high. The skeleton material is a steel frame, which has strong resistance to wind, rain, and snow. The shed film is a polyvinyl chloride drip-free film with a thickness of 0.1mm±0.02mm and a certain load-bearing capacity. The greenhouse must have cold-proof, heat-insulating and warming facilities. The shed is installed in the direction of sitting north and facing south, which is conducive to warming.

[0035] 3) Disinfection of the seedling shed: Disinfect the seedling shed 15 days before sowing. Use 150 times 2% chlorine dioxide solution to spray the walls, ground, greenhouse frame, old film, etc. inside the shed and seal it for 2 to 3 days after spraying. Use 3% lime water or 5% bleaching powder to spray the ground, walkways, and drainage ditches outside the shed.

[0036] In addition, the walls, ground, greenhouse frames and old films in the seedling shed can also be disinfected with 0.1% to 0.5% potassium permanganate or 20 times diluted 30% effective chlorine bleach, or fumigated with chlorothalonil aerosol and potassium permanganate for more than 24 hours, or spray disinfectant with 50 times diluted 49% formaldehyde (formalin).

[0037] 4) Install insect-proof nets. Use commercially available 60-mesh insect-proof nets and install them at the upper and lower vents of the seedling shed to prevent aphids from flying into the tobacco seedling shed in the Northeast region and eating the tobacco seedlings, thereby reducing the incidence of tobacco seedlings.

[0038] 5) Water reservoir production: a water reservoir is built in the seedling shed with red bricks, with a fixed length of 4 meters, a fixed width of 2.5 meters, and a depth of 35 centimeters. The pool is covered with intact new black polyethylene film and fixed with soil around the film to increase the water temperature required for seedling cultivation and reduce the low temperature damage to tobacco seedlings caused by the low water temperature in the cold Northeast region. 10 days before sowing, fill the reservoir dug in the seedling shed with clean water, increase the water temperature for standby use, and the water temperature is 9 to 11°C. The water in the reservoir should be replenished in time. The water used for seedling cultivation must be clean, pollution-free, and neutral in pH. Non-tap water must be disinfected with bleaching powder 10-15g / t before use. It is forbidden to use polluted water sources such as ponds and drainage ditches.

[0039] 6) Production of nursery pools. Nursery pools are made in nursery sheds. The length of a single pool is fixed at 6 meters, the width is fixed at 2 meters, the depth is 1.6 centimeters, and it is built with red bricks on all sides. The pool bottom is leveled using the nursery bed leveler independently developed by the applicant (see patent ZL202021682045.9 for equipment information). A 5cm to 10cm high small earth ridge is built on the four sides of the nursery bed (near the back wall, south side, and the sides of the east and west gables). The remaining aisles and nursery pools are lightly pressed and fixed with red bricks at an interval of 20 centimeters, and the nursery bed is enclosed into several small pools (see Figure 1 ).

[0040] 7) Laying the membrane: Use intact new black polyethylene film to lay on the bottom of the pool. Firmly compact the membrane with soil around it, then put it in 1-1.5cm deep water to test the pool surface level and leakage. If the pool membrane leaks or the horizontal drop of the pool bottom is too large (more than 3mm), the pool surface needs to be leveled again and the membrane needs to be replaced.

[0041] 8) Fill the nursery pool with water for nursery. One week before sowing, fill the nursery pool with water prepared in the reservoir in the greenhouse. The water depth of the nursery pool should be about 1.5 cm (see Figure 2 ).

[0042] 9) Matrix filling. The matrix is ​​mainly composed of materials rich in organic matter, such as peat, peat, carbonized or decomposed crop residues, vermiculite, expanded perlite, etc. The physical properties of the matrix are determined by the organic matter content, matrix bulk density, total porosity, capillary porosity, matrix particle size, etc. in the matrix material. The specific physical and chemical properties are shown in Table 1. The matrix is ​​evenly loaded into the plastic seedling tray.

[0043] Table 1 Physical and chemical indicators of flue-cured tobacco floating seedling medium

[0044]

[0045] 10) Sowing, the sowing time is March 5-16, and the seedling age is about 50 days. Use a seeder for sowing, which has the function of pressing holes and sowing. Sow 1-2 coated seeds in each seedling hole, with a spacing of 0.5 cm. Sow 2 seeds in the two long sides of the seedling tray. The sowing depth is controlled at 0.3-0.5 cm. After sowing, sprinkle 2-4 mm of soil evenly on the tray. Put the seedling tray steadily into the pool to allow the seed coating to fully absorb water and lyse.

[0046] 11) Seedling management

[0047] Seedling shed ventilation:

[0048] Ensure ventilation in the greenhouse from 8 to 16 o'clock every day to maintain the temperature in the greenhouse at 25-30℃ and the humidity at 70%.

[0049] Moisture Control and Covering Substrate:

[0050] 4-5 days after sowing, drain the water in the nursery pool, and then cover the entire nursery tray with a layer of nursery substrate. 2-3 days later, add the nursery water in the reservoir to the nursery pool, and then cycle twice through the process of draining water, covering the nursery substrate, and storing water. Then, only store water and drain water, and no longer cover the nursery substrate. The specific water storage and drainage operations are: drain the water in the nursery pool again after 4-5 days, and add the nursery water in the reservoir to the nursery pool after 2-3 days, and cycle for many times until 7-10 days before transplantation. The thickness of each covering substrate is 0.5 to 1.5 mm, and the water depth of the nursery pool is about 1.5 cm after each water storage.

[0051] Disease control:

[0052] For anthracnose, spray 600 times diluted 80% mancozeb powder; for damping-off, spray 600 times diluted 58% metalaxyl mancozeb wettable powder; for mosaic disease, use antiviral agents to prevent common mosaic disease in the seedbed; spray once every 10 days.

[0053] Anthracnose can also be treated by spraying 800 times diluted 80% thiophanate-methyl powder or 500 times diluted 25% carbendazim.

[0054] Damping-off disease can also be treated by spraying 1000 times diluted 50% thiophanate-methyl wettable powder or 1000 times diluted 75% thiophanate-methyl wettable powder.

[0055] top dressing:

[0056] Choose diammonium phosphate as the seedling fertilizer, and add fertilizer three times to increase the stress resistance of tobacco seedlings. The specific operation is: dissolve diammonium phosphate in water, and add fertilizer to the seedling pool while filling the seedling pool with water. The first time of adding fertilizer is about 15 to 16 days after sowing; the second time of adding fertilizer is about 27 to 28 days after sowing (the first two times are topdressing in the water of the seedling pool); the third time of adding fertilizer is 35 to 36 days after sowing, and it is topdressed according to the growth of tobacco seedlings (change water and fertilizer from the seedbed, spray the tobacco seedlings with clean water after fertilization, and wash off the foliar fertilizer). The amount of topdressing for a single time is set at 200 grams per 10,000 seedlings (see the picture after emergence). Figure 3 ).

[0057] 12) Preparation for transplanting: drain the water in the nursery pool 7 to 10 days before transplanting, and do not add water or fertilizer to the nursery pool. Use a watering can to add water instead. Generally, water once or twice a day on sunny days. The specific number depends on weather conditions. It is best to make the substrate wet but not leak downwards. Water control and seedling hardening should be carried out gradually 7 to 10 days before transplanting. The degree of water control should be such that the tobacco seedlings wilt slightly at noon and recover in the morning and evening. Open the vents under the greenhouse 5 days before transplanting to ventilate the tobacco seedlings so that they can adapt to the external climate. Spray the tobacco seedling inhibitor 1 day before transplanting to protect the tobacco seedlings, and move the tobacco seedlings into the field for planting. The emergence rate of tobacco seedlings is 96%.

[0058] Comparative Example 1

[0059] The floating seedling raising method is used for raising seedlings, which is different from Example 1 in that: in step 11), the moisture control and substrate covering process of seedling raising management, the floating seedling raising does not need to cover the seedling raising substrate again, and the water in the seedling raising pool is not discharged during the floating seedling raising process. During the floating seedling raising process, there is always water in the seedling raising pool, and the water depth is about 1.5 cm. In addition, step 12) floating seedling raising is to cut the leaves and harden the seedlings by a leaf shearing machine, and cutting the leaves and hardening the seedlings will cause wounds to the tobacco seedlings, which are easy to spread diseases.

[0060] Comparative Example 2:

[0061] The wet seedling raising method is used for seedling raising, which is different from Example 1 in that: 11) in the process of moisture control and covering the substrate in seedling raising management, the wet seedling raising does not need to cover the seedling raising substrate again. Before the big cross stage of the tobacco seedlings, the water in the seedling raising pool is ensured to be continuous, with a water depth of about 1.5 cm; after the big cross stage of the tobacco seedlings, the water in the seedling raising pool is cut off, and the substrate is kept moist by sprinkling or spraying water until 7 to 10 days before transplantation.

[0062] Comparative Example 3:

[0063] The seedling raising method adopts the tidal seedling raising method, which is different from Example 1 in that: tidal irrigation equipment needs to be built in the early stage of seedling raising; 11) Water control and substrate covering process of seedling raising management, tidal seedling raising does not need to cover the seedling raising substrate again, from sowing to seedling emergence, the water depth of the seedling raising pool is controlled at 4 cm, and the seedling raising tray is placed in the seedling raising pool to continuously draw water; tidal water control is adopted from the seedling emergence stage to the seedling stage, and water is supplied to the seedling raising pool three times a day. From the seedling emergence stage to the seedling stage, each time the water is supplied for 20 minutes, the seedling raising tray draws water for 1 hour, and the water is drained for 20 minutes; water is supplied at 8 am, 12 noon, and 18 pm respectively; from the seedling emergence stage to the small cross stage, the water depth of the seedling raising pool is controlled at 4 cm; from the small cross stage to the large cross stage, the water depth of the seedling raising pool is controlled at 3 cm; from the large cross stage to the seedling stage, the water depth of the seedling raising pool is controlled at 3 cm; until 7 to 10 days before transplantation.

[0064] Comparative Example 4

[0065] The difference from Example 1 is: 9) Matrix filling, in Example 4, the matrix is ​​filled to a height of 1 / 2 of the hole depth; 11) Moisture control and matrix covering process of seedling management, in Example 4, the water in the seedling pool is drained 4-5 days after sowing, and water is stored in the seedling pool 2-3 days later, and the cycle is alternated until 7-10 days before transplanting, and when the growth point of the tobacco seedlings is higher than the plate surface of the seedling tray with holes, half of the tobacco leaves are removed, and the matrix is ​​filled for the second time on the third day after cutting the leaves to fill the seedling holes.

[0066] 100 tobacco seedlings of Example 1 and Comparative Examples 1-4 were randomly selected to obtain experimental data (see Table 2).

[0067] Table 2 Comparison of seedling quality in Northeast China between the seedling raising method of Example 1 of the present invention and Comparative Examples 1-4

[0068]

[0069] Note: The incidence rate of moss is the percentage of green algae occurrence in the nursery holes to the total number of nursery holes tested;

[0070] The moss mortality rate is the proportion of tobacco seedlings that die due to moss invasion.

[0071] It can be clearly seen from the test results of the tobacco seedlings in the seedling stage that the method of the present invention not only has a high emergence rate, but also has good root development. Comparative Example 1 floating seedlings and Comparative Example 2 wet seedlings have not achieved the effect of alternating dry and wet conditions due to the continuous water supply in the seedling pool, resulting in the appearance of a large number of green algae, and due to the long-term soaking of the root system in the water, the tobacco seedlings are of different sizes. The floating seedlings need to float in the water for a long time, and the seedlings can only be hardened by cutting leaves with a leaf shearing machine, and cutting leaves and hardening seedlings will cause wounds to the tobacco seedlings, which are easy to spread diseases. The dry and wet alternating seedling method of the present invention can achieve hardening by controlling the growth of tobacco seedlings through drainage. Comparative Example 3 tidal seedlings can achieve dry and wet alternation by using tidal water control from the emergence stage to the seedling stage, but because water is supplied and drained three times a day, it is too frequent, the dry and wet effect is not obvious, and the final effect is not ideal, and tidal irrigation equipment needs to be built in the early stage of seedling cultivation, which is complicated to operate. The timing of covering the substrate in the seedbed of Comparative Example 4 is different from that of the present application, and the seedling effect of alternating dry and wet conditions in the present application cannot be achieved, and the result is not ideal.

[0072] The above embodiments are only preferred implementation modes of the present invention. It should be pointed out that for those skilled in the art, several modifications and improvements can be made without departing from the structure of the present invention, such as simply adjusting the seedling shed disinfection method, sowing method, topdressing method, etc. These will not affect the effect of the implementation of the present invention and the practicality of the patent.

Claims

1. A dry-wet alternating flue-cured tobacco seedling raising method suitable for the Northeast region, characterized in that: (1) Seedling preparation Choose a location that is leeward and sunny as the nursery ground, build a warm shed for wintering as the nursery shed, and set up a reservoir in the nursery shed to increase the water temperature for nursery; (2) Preparation of nursery pond Make multiple seedling raising pools in the seedling raising shed, the bottom of the seedling raising pools is flat, and the seedling raising pools are filled with seedling raising water from the reservoir; (3) Seedling cultivation process Put the seedling tray containing flue-cured tobacco seeds into the seedling pool; ventilate the seedling shed every day, first treat the seedling pool multiple times 1, and then treat it multiple times 2 during the seedling raising process until 7 to 10 days before transplanting; carry out disease resistance treatment, apply topdressing 3 times during the seedling raising period, cut off the fertilizer and water in the seedling bed 7 to 10 days before transplanting to control water and harden the seedlings, and move the flue-cured tobacco seedlings into the field for planting; The treatment 1 is drainage-covering seedling medium-water storage treatment; The treatment 2 is a drainage-water storage treatment.

2. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The drainage-covering seedling medium-water storage treatment is to drain the water in the seedling pool 4 to 5 days after sowing, then cover the entire seedling tray with a layer of seedling medium, and add seedling water to the seedling pool 2 to 3 days later; the multiple treatments 1 are 3 treatments 1; The drainage-water storage treatment is to drain the water in the nursery pond again after 4 to 5 days, and to add nursery water to the nursery pond after 2 to 3 days.

3. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The seedling raising shed is a civil construction structure and a steel frame, and the shed film is a polyvinyl chloride drip-free film, and the shed film is covered with heat preservation and warming facilities.

4. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The bottom of the nursery pond is paved with a black polyethylene film, which is compacted and fixed with soil around it to ensure that the nursery pond is watertight. The nursery pond is filled with nursery water prepared in a reservoir. After the nursery pond is filled with clean water, the water depth is about 1.5 cm.

5. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The seedling tray containing flue-cured tobacco seeds is provided with a seedling substrate in the seedling tray, sowing seeds in the seedling substrate, and after sowing, evenly sprinkling 2-4 mm of covering soil on the seedling substrate in the seedling tray; The sowing is carried out by using a seeder with self-contained hole pressing and sowing functions, 1 to 2 coated seeds are sown in each seedling hole, 2 seeds are sown in the two long side seedling holes of the seedling tray, the sowing depth is controlled at 0.3 to 0.5 cm, and after sowing, 2 to 4 mm of covering soil is evenly sprinkled above the tray.

6. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The seedling raising shed is ventilated from 8 to 16 o'clock every day, and the temperature in the shed is maintained at 25 to 30° C. and the humidity is 70%.

7. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The disease resistance treatment is to spray 600 times diluted 80% mancozeb powder, 800 times diluted 80% thiophanate-methyl powder or 500 times diluted 25% carbendazim to prevent and control anthracnose, and to spray 600 times diluted 58% metalaxyl mancozeb wettable powder, 1000 times diluted 50% thiophanate-methyl wettable powder or 1000 times diluted 75% thiophanate-methyl wettable powder to prevent and control damping-off disease; use antiviral agents to prevent mosaic disease; spray once every 10 days.

8. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The topdressing is to select diammonium phosphate as a seedling fertilizer, which is applied three times to increase the stress resistance of tobacco seedlings.

9. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 8, characterized in that: The specific steps of topdressing are: dissolving diammonium phosphate in water, and fertilizing the seedling pool while filling the seedling pool with water, the first time of fertilizing is selected between 15 and 16 days after sowing; the second time of fertilizing is between 27 and 28 days after sowing; the third time of fertilizing is between 35 and 36 days after sowing, water and fertilizer are added from the seedbed, and clean water is used to spray the tobacco seedlings after fertilizing, and the amount of topdressing is 200 grams per 10,000 seedlings.

10. The dry-wet alternating flue-cured tobacco seedling raising method according to claim 1, characterized in that: The water control and seedling hardening are carried out gradually 7 to 10 days before transplanting, and the degree of water control is appropriate to make the tobacco seedlings slightly wilt at noon and recover in the morning and evening; 5 days before transplanting, the vents under the greenhouse are opened for ventilation to allow the tobacco seedlings to adapt to the external climate; 1 day before transplanting, the tobacco seedlings are sprayed with an inhibitory agent to protect the tobacco seedlings.

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