Most vegetables require strong light conditions. However, in winter, especially in cloudy and rainy weather, the light is weak. The lack of light in greenhouse vegetables is a common problem. Insufficient illumination not only fails to produce more lush photosynthetic activity, but also reduces transpiration and the plants grow weakly, which affects the yield and character of the vegetables. Such as low light conditions, tomato pollen dissipated, infertility; eggplant emerged short-inflorescence shape, affecting pollination; loofah and watermelon and other vegetable plants in vivo malnutrition, resulting in falling flowers and fruit.
Some experts call these scenes "light hunger." How to prevent “starvation†in winter vegetables?
1. Cultivation methods to improve light conditions Some cultivation techniques can obviously improve lighting conditions in the shed, such as vegetables to take the north and south direction, the same large row spacing and small row spacing, so that all lines can get better light conditions; melon vegetables, eggplant Vegetables, such as through pruning, old leaf removal, timely binding of vines and other methods, adjust the plant light conditions, can play a better "grace" role.
2. The use of high quality non-drop film and maintain the quality of smooth clean film will affect the light intensity of the shed, high quality non-drop film transmittance is high, not easy to pollute dust; poor quality non-drip film is easy to aging, vulnerable to pollution, light transmittance Then fell. The drop-free film transmittance also decreases with longer use time. According to the measurement, within 13 days after the new high-quality non-drip film, the transmittance of the film at noon reached 93%. After 73 days, the light transmittance of the film was reduced to 81%.
Therefore, often scrubbing the shed film and maintaining the smoothness of the shed film is one of the important measures to prevent “starvation†in greenhouse vegetables. The use of one year's shed film, the light transmittance is usually reduced by 30% -40%, for cucumbers, melons other than melon vegetables, such as eggplant, vegetables, beans, vegetables and other light intensity of the more demanding greenhouse vegetables Production, it is best to change the new high-quality non-drip film.
3. The use of reflective screens in the shed In the greenhouse wall or the south side of the rear pillar, Zhang Gui polyester film is used as a light curtain, which can obviously “graceâ€. According to observations, at 11 o'clock noon, the ground plane within 3 meters from the light curtain, even than the shed without a light curtain, increased the light intensity by 0.7 million lux, increased the utilization rate of light energy by 25.2%, and measured the intensity of light increase by 0.69 million lux at 14 o'clock. Increase the utilization of light energy by 23.4%. At the same time can increase the ground temperature 1 °C -2.5 °C.
Specific use: In the first half of the first year of November, the curtain of light was opened and removed in mid-April of the following year. Hang the length as required, measure out two equal-length light curtains, and glue the two light curtains together with a transparent tape to form a 2-meter-wide banner. Pull the two east-west fine wires in the upper front of the column in the greenhouse. Wrap the wire on the upper and lower edges of the screen back about 3 cm and fix it with a transparent tape or paper clip.
The light curtain can also be directly fixed on the back wall (remaining vents must be left). Pay attention to: Underneath the curtain of reflection, leave a gap to facilitate watering; places that are close to the light curtain must be properly watered; in a greenhouse, seedlings should be kept 50 centimeters away from the light curtain to prevent burning.
4, timely removal of shed film droplets of water droplets can strongly absorb, reflect the sun's rays, according to information, severe light transmittance can be reduced by about 50%. Therefore, the elimination of water droplets and water film on the membrane is one of the effective ways to enhance the light. The specific methods are as follows: 1) Non-drop film or three-layer composite film is selected.
2) Wipe with a clean rag.
3) The film must be covered, the film should be filled with water, and the air humidity should be controlled.
4) After the watering, close the shed for 1 hour and release the air to remove moisture.
5) Set up a windbreak to reduce the temperature difference between the shed and the outside environment.
5. The mulching of the mulching film usually has a better effect of warming, water-preserving, and soil consolidation, and it also has a good “grace†effect. Because of the reflective effect of the water droplets attached to the surface of the mulch and the plastic film, the reflected light and scattered light near the ground can be enhanced by 50%-70%. For peppers, eggplants, tomatoes, etc., the lighting conditions can be improved, and the soil temperature can also be increased. . In the mulch, milky white and silver-gray films reflect more, the transparent film is centered, and the green and black films are less reflective.
In the stage of growing vegetables in greenhouses, it was obvious that in the previous medium-term growth, it was not obvious after sealing. Therefore, in the middle of greenhouse vegetables in the mid-term increase in temperature, can be covered with milky white film or silver-gray film (also the role of flooding) or transparent film.
6, to maintain the cleanliness of the general new film transmittance of up to 80 ~ 88%, but after covering a period of time, due to pollution and aging, light transmittance will change. Water droplets and dust on the shed film have a great influence on the lighting in the shed. According to observations, a layer of water droplets is attached to the film, which can reduce the light transmittance by 20 to 30%. After the new film was used for 2 days, 10 days and 15 days, the light in the shed could be weakened by 14%, 25%, and 28% in turn because of the contamination with dust.
Therefore, the water droplets and dust on the shed film should be cleaned and cleaned frequently. After snow, the snow should be removed in time to increase the transparency and the amount of light. The greenhouses ventilate for half an hour after sunrise to reduce the amount of water on the membrane surface, thus increasing the light transmittance.
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