First of all, it is very important to choose a good seedling substrate.

There are many preparations before sowing, such as seedbed preparation, substrate preparation and seed treatment. In recent years, with the continuous improvement and perfection of cultivation facilities, many tasks such as seed treatment and germination no longer need to be done by melon farmers themselves, but can be handed over to seed dealers. But some work, such as substrate disinfection, can not be ignored, which is the first step to cultivate healthy and strong seedlings.

You must be careful when choosing seedling substrates, and don't buy inferior seedling substrates to save a few dollars. After the substrate is bought back, it must be disinfected, sterilized and insect-proof in advance before it can be used with confidence.

Second, prevent the scion from being covered.

When watermelon seedlings are unearthed, they are brought out of the ground together with the seed coat, which makes the cotyledons unable to stretch in time. This phenomenon is called "unearthed with shells" (melon farmers call it "capping"). When watermelon seedlings are unearthed with shells, cotyledons can't unfold, which will affect the photosynthesis of cotyledons, or turn yellow, wither or form "tall seedlings", which is extremely unfavorable for cultivating strong seedlings.

In order to reduce the number of scions with caps, we can start from the following aspects:

1, the soaking time should be prolonged appropriately, and no dry core can be seen when the seed center is cut open. Generally, it is appropriate to soak large seeds for 10- 12 hours and small seeds for 8- 10 hours.

2. After sowing, it is found that there is too little covering soil, so it can be covered with a layer of fine soil or nutrient soil.

3. When the soil is dry, you can spray the sun-dried warm water with a watering can, but you should pay attention to spraying it once, not repeatedly, and you should not pour "blindfold water".

4, artificial hulling, once the unearthed seedlings with shells are sent out, artificial hulling should be carried out in time. In the morning or after proper watering, when the seed coat is wet and soft, hold the seedling with your left hand, gently push the seed coat with your right hand, and slowly pull out the cotyledons.

Third, strengthen warm-keeping measures to prevent low-temperature obstacles.

Watermelon seedling stage, namely 65438+February-February, is the coldest period in winter, especially before and after grafting. However, many melon farmers often encounter low temperature obstacles when they encounter cold current because of the small seedling shed, imperfect insulation facilities and low temperature in the shed. The temperature in the shed is low, so it is necessary to improve the thermal insulation of the seedling shed. In addition, improving the cold resistance of seedlings is also an important measure to deal with low temperature.

1, measures to strengthen heat preservation and heating facilities

In addition to the original insulation measures such as covering the shed film and insulation quilt, it is also very necessary to keep warm properly in the shed. Be sure to prepare for protection to avoid injury to seedlings.

In addition, in order to cultivate strong seedlings, it is suggested to install supplementary light lamps in the shed, which can give attention to both heating and supplementary light, and has outstanding effect on improving seedling quality. In case of short-term cooling due to cold wave, greenhouse heating blocks can be used for short-term heating, and a seedling greenhouse can use 2-4 blocks. After ignition, it can burn continuously for 2.5 hours, the temperature will continue to rise, and there is no open flame, so it is safe to use and quickly increase the night temperature above 5℃.

Through the combination of various measures, the light and temperature conditions of seedlings can be effectively improved, and the primary factors restricting the success or failure of seedling raising can be solved.

2. Improve the cold resistance of seedlings.

After emergence, spraying 1000 times of suspended calcium, 1000 times of chitin and 300 times of white sugar on leaves can effectively improve cell activity and enhance the stress resistance of seedlings. According to teacher Yu Huagen, director of China Plant Protection Association, calcium fertilizer can be said to be the best antifreeze, which can improve cell membrane activity and reduce the impact of freezing injury. ?

Extended data:

Field diagnosis of watermelon seedling stage;

1, cotyledons and true leaves are small, dark and dull, with short internodes between hypocotyl and stem base and slow growth. This is mainly due to the low temperature of seedbed. The management measure is to increase the bed temperature, and if it is a hotbed, it can be heated appropriately; If it is a cold bed, open the straw mat to receive the sunshine during the day and cover it at night to keep warm.

2. True leaves are small and yellow and grow slowly. If the bed temperature is normal, it is caused by lack of fertilizer. Foliar fertilizer can be sprayed in time to relieve the symptoms of fertilizer deficiency.

3. The leaves are dark green and grow slowly. If the bed temperature is normal, it is a symptom of water shortage, which often appears in various hotbeds. When this kind of seedling appears, water it in time.

4. Cotyledons are thin, dark green in color, and hypocotyls are short and thick and garlic-like, which is the manifestation of fertilizer damage or drug damage. At this time, it is necessary to properly water more and spray Wanshuai No.1 (cytokinin) to reduce fertilizer damage or drug damage.

5, cotyledons are upturned, true leaves are small, yellow in color, rolled up, some edges are dry, and the whole leaves are dead. This is the performance of high temperature scalding seedlings, so it is necessary to ventilate and cool down in time, and the highest temperature in the bed should not exceed 35℃. In case of sunny days, pay attention to uncovering the film and ventilation to prevent the seedlings from burning.

6. Cotyledons and true leaves are large and thin, light green in color, and hypocotyls are thin and long, which is the performance of excessive seedlings. It is necessary to strengthen ventilation, reduce the temperature, especially at night, control watering, uncover the plastic film in time during the day and increase the light.

7. White edges appear on the cotyledon edges, or the true leaf edges are dry and spoon-shaped, with serious stomata. Mainly due to excessive ventilation in the seedbed, the temperature and humidity in the bed plummeted, the leaf edge quickly lost water, and the leaf cells were damaged and dried up. In order to prevent the occurrence of such seedlings, ventilation should be started when the temperature in the bed is 25℃ in the morning, not when the temperature rises very high; Vents should be opened on the downwind side and gradually increase from small to large.

8. Dark brown root system is the phenomenon of root system retting caused by high humidity and low temperature of seedbed; Rusty yellow root system is the expression of bed soil drought and root system aging.

9. Freezing injury often whitens the edges of cotyledons and true leaves. In heavier cases, the true leaves are dry, only the growing points are reserved, and the strong seedlings become weak seedlings, or there is a phenomenon of "headless seedlings". In severe cases, the whole plant turns black and dies of freezing. Therefore, we must practice seedlings at low temperature before planting, often listen to the weather forecast, and take temporary heating and emergency anti-freezing measures before the cold current comes. Don't expose the greenhouse film immediately in the morning after slight freezing injury or cold injury, so as to avoid the temperature rising too fast after the sun comes out, which will make the leaves lose water and wilt, and should gradually expose the greenhouse film.

References:

Baidu encyclopedia: watermelon