How to manage the temperature and humidity in winter and spring seedling raising of solanaceous vegetables?

The suitable temperature for the growth of solanaceous vegetable seedlings is about 20℃ during the day and 65438 00℃ at night. The root system began to grow when the soil temperature was 7 ~ 8℃, and the optimum temperature was 20 ~ 25℃. The relative humidity of seedbed air should be 60% ~ 80%. In the temperature and humidity management of seedlings in winter and spring, we must attach great importance to the temperature and humidity conditions of the root system (soil), because the root system is the foundation and the root system is not long enough, a series of problems will occur.

On the other hand, ventilation can adjust the temperature and humidity in the seedbed, promote the transpiration and absorption of seedlings, exercise the ability of seedlings to adapt to the external environment, improve the ability of cold resistance and disease resistance, and inhibit the activities of pathogens in the seedbed. Therefore, the temperature and humidity management in the seedbed in winter and spring is mostly carried out through ventilation.

(1) Temperature management Eggplant vegetables require high temperature and high humidity after sowing and before emergence, and generally do not need ventilation. When about 70% of seedlings are unearthed, ventilation should be started, and the temperature of seedbed should be gradually reduced to 20 ~ 22℃. At this time, if the temperature is not lowered in time, it is easy to grow into weak and tender seedlings and collapse. When the cotyledons of seedlings elongate and turn green, the bed temperature is maintained at 15 ~ 20℃.

Generally, in the morning, when the weeding curtain is opened and water vapor appears in the plastic film of the seedbed, ventilation can be started; At 3 ~ 4 pm, when the temperature drops gradually, it must be covered again and the ventilation should be stopped.

The length of ventilation time and the size of ventilation openings should be adjusted at any time according to the weather and seedling growth. On days of severe cold and strong northwest wind, special attention should be paid to the degree and mode of ventilation.

It's warm and windless at noon on a sunny day, so you can uncover all the plastic films and let the seedlings shine more directly in the sun; There is a northwest wind on cloudy days, so it is advisable to have a small ventilation around noon, and the tuyere is covered with a straw curtain to prevent cold air from blowing on the bed. Ventilation is dominant in normal night, but the tuyere is smaller than during the day; When it is cold and snowy, it can be slightly ventilated or not; In rainy and snowy weather, proper ventilation should be given according to the temperature and humidity of the seedbed.

After entering the middle and late February, the weather gradually warms up, and the seedlings grow rapidly, which is easy to grow in vain. It is necessary to strengthen ventilation and keep the bed temperature at 10 ~ 15℃, but the temperature should not be too low, otherwise it will affect the flower bud differentiation.

It should be noted that in cold weather, air convection in the seedbed should be avoided during ventilation and cooling, so as to prevent cold air from blowing directly into the seedbed, otherwise freezing injury or chilling injury will easily occur.

(2) Humidity management After emergence, ventilation is adopted to cool down, and at the same time, the temperature and humidity in the seedbed are reduced, which meets the requirements of healthy growth of seedlings. If the bed soil is too wet after emergence, the roots of seedlings will be less. Because the roots of seedlings not only need to absorb water and nutrients in the seedbed soil, but also need air to breathe, the gaps in the soil are occupied more, and the air is less, which hinders the root system from breathing, and the root system will not grow well.

In high humidity soil, the temperature is not easy to rise. If the soil temperature is low and the humidity is high, it will further hinder the growth of roots. The root system of seedlings is poorly developed, and stems, leaves and buds naturally grow poorly, becoming weak seedlings. This weak seedling is not only easy to get sick, but also has adverse effects on future maturity and yield. It is for this reason that seedlings are easy to collapse in seedbeds with low soil temperature, high humidity and soil hardening. In addition, the high air humidity in the bed also hinders the transpiration of seedlings, making them unable to grow healthily and prone to diseases such as early blight, gray mold and anthracnose.

It is not good that the bed soil humidity is too high after emergence, and it is not ideal that the humidity is too low. Because seedlings need water for photosynthesis, transpiration and other physiological activities, fertilizers and nutrients in soil also need to be dissolved in water before they can be absorbed and utilized by roots. So the seedbed is too dry, the seedlings can't get enough water, and the growth is inhibited, which leads to the stiffness of the seedlings. Nevertheless, in actual production, it is mainly to prevent the humidity of seedbed from being too high, not too low (except in a few cases). Due to the low temperature and rainy weather in winter and spring, it is not only easy to have high humidity, but also more troublesome to reduce humidity if the humidity in the seedbed is too high.

In order to prevent the humidity of the seedbed from being too high, the seedbed should be located in a place with high terrain and convenient drainage. When making a seedbed, the soil surface of the seedbed should be higher than the surrounding ground, and a drainage ditch should be opened around the seedbed to prevent water accumulation. In the process of seedling raising, the humidity of seedbed is mainly reduced by ventilation, water control, spreading dry soil and loosening soil. The ventilation method is the same as the above-mentioned temperature and light management (synchronization), and the control of watering will be described below. Only dry soil and loose soil are introduced here.

(1) When spreading dry soil to raise seedlings, spreading loose and fertile fine soil on the surface of bed soil is called spreading soil. After spreading a layer of loose fine soil on the surface of bed soil, it can prevent the moisture in the soil below from rising to the surface, so it can reduce moisture evaporation and keep the soil moist. Sowing soil after watering seedbed can enhance watering effect, reduce watering times and prevent soil hardening. Because the loose fine soil spread on the surface of bed soil is easy to dry, it is easy to raise the soil temperature, thus promoting the growth of seedling roots.

When the humidity of seedbed is too high, spreading dry soil can reduce the humidity to some extent. This fine and dry soil is usually prepared in advance. Spreading soil can not only adjust the humidity of seedbed, but also make the part of seedling hypocotyl buried in soil produce fibrous roots and enhance the absorption capacity, which is especially obvious for tomato seedlings.

In some special cases, such as the bed soil is dry, but it is not suitable for watering (to prevent the spread of diseases or the arrival of cold air), wet and fertile fine soil can be sprinkled on the bed soil; Spreading wet fine soil during seedling emergence can not only adjust the moisture of topsoil and prevent seedlings from "topping", but also fill the gap formed by soil around seedlings during seedling emergence, reduce root damage and prevent seedlings from lodging. Sprinkling this wet soil after each seedling is deleted has this effect.

It should be noted that the leaves and growing points of seedlings should not be polluted when spreading soil. Therefore, soil should be spread when the stems and leaves of seedlings are dry. Generally, the thickness of a soil spread is about 0.5 cm. When the soil temperature is low, if the soil is spread too thick at one time, the soil temperature at the root of the seedling is not easy to rise.

(2) loosening the soil during seedling raising means loosening the surface of the bed soil to prevent hardening. Because the water in the bed soil rises to the soil surface along the capillaries between soil particles. Looseness destroyed the capillaries on the surface, so the water could not continue to rise. Therefore, loosening the soil can prevent the water in the bed soil from rising to the soil surface, which can reduce the evaporation of water and maintain the humidity of the bed soil. At the same time, loosening the soil can make the air containing more carbon dioxide easily discharged from the soil, and make the fresh air containing more oxygen penetrate into the soil, thus promoting the respiration of the roots. Loosening can also promote the activities of beneficial microorganisms in bed soil and improve soil fertility. If there are weeds in the seedbed, you can carve them out by loosening the soil.

After watering, loosen the soil after the soil surface is slightly dry, which can fully maintain the moisture of the bed soil and reduce the watering times. Loosening can not only keep enough water in the bed soil for root system to absorb, but also keep the surface of the bed soil loose and dry, which has a good effect on preventing collapse.

When loosening soil, bamboo sticks are often used to pry open the topsoil between seedlings, or small iron harrows made of iron and iron wires are used to loosen the topsoil between seedlings. However, the scarification should not be too deep, so as not to damage the root system of seedlings.