The sowing seedling period of autumn lettuce is in the high temperature season, the temperature difference between day and night is small, the night temperature is high, the respiration is strong, and it is easy to grow. At the same time, because of the high temperature and long sunshine, the lettuce flower buds are rapidly differentiated and convoked, so the seedlings are strengthened and the auxiliaries are prevented. Twitching is the key to the cultivation of autumn lettuce.

Selection

Choose a variety that is resistant to heat and convulsions. The autumn lettuce shoots are in the high temperature and long sunshine conditions that are conducive to convulsions. Therefore, it is necessary to select mid-late and late-maturing varieties of the tip-type, such as purple scent, willow lettuce, and Wannianchun, which are slow to respond to high temperature and long sunshine.

Sowing off

It takes three months from the sowing to harvesting of autumn lettuce. The suitable temperature for the growth of stems and leaves is about 60 days after the average temperature drops to 21 °C. Therefore, the average temperature in the seedling stage should be reduced to 21 °C~22. The previous month at °C is safer. Although the sowing date is too late, it is not easy to convulsion, but the yield is reduced due to the short growing season.

Nursery off

In summer, it is difficult to germination due to high temperature. Before sowing, it is necessary to soak the seeds at low temperature. The method is to soak them in cold water for a day and night and then put them at a temperature of 15 °C to 20 °C. After germination for 3 to 4 days, they are sown at a low temperature in the afternoon. After sowing, cover the wheat straw, straw and other shades on the surface to achieve the purpose of moisturizing, cooling and rainproof. It can also be mixed with pakchoi, and the pakchoi can be used to cover the lettuce for shading. After the lettuce is released, the cabbage is gradually removed.

There are two methods of sowing: wet and dry. When the seedlings are topped with the wet sowing method, the water is sprinkled once, and after 1 to 2 days, it is released. For dry sowing, water must be sprayed frequently to keep the soil moist and lower the ground temperature. Note that the water spray must be carried out in the morning and evening. After emergence, gradually remove the cover and strengthen the training of the seedlings. After that, the water is first poured to reduce the temperature of the seedbed to prevent the seedlings from being sunburned. After that, the water should be poured frequently to keep the soil moist. After the rain, the well water is poured in time to reduce the temperature and prevent the dead seedlings. Timely weeding, insect control, and seedlings, 3 to 4 true leaves, with a quick-acting nitrogen fertilizer applied with water.

Management

The seedling age is 25 to 30 days, and there are 4 to 5 true leaves when planting. It is best to plant the soil in the afternoon to facilitate the seedlings. Before the planting, the base fertilizer must be applied. In order to prevent the autumn lettuce from twitching, the water and fertilizer requirements must be met as much as possible to make the leaf area expand rapidly. After planting, shallow pouring and pouring until the seedlings are slowed down, a quick-acting nitrogen fertilizer is applied after the seedlings are slowed down, and then the watering is appropriately reduced, and a deep cultivating is carried out to extend the root system. The second top dressing is carried out when the group is planted, which accelerates the occurrence of the leaves and enlarges the leaf area. Before the ridge is closed, the third top dressing will be carried out when the stem begins to expand. In addition to applying the quick-acting nitrogen fertilizer, the potassium fertilizer should be added to promote the stem enlargement.

Adjustment

Uncultivated convulsions are inhibited by plant growth regulators. When the stem is thickened before the lettuce is closed, it can be sprayed 2 or 3 times with the chlormequat or the fresh leaf surface, which can effectively inhibit the convulsion and increase the stem weight.