Greenhouse cultivation needs to pay attention to "four major factors"
Adequate light, carbon dioxide, water and temperature are necessary for plant growth. How to ensure the balance of these factors in the special environment of greenhouses?
Ensure adequate light
Sufficient illumination is the guarantee of high yield of greenhouse crops. In the winter warm plastic greenhouse without artificial heating, insufficient light is a major factor limiting production. The data shows that the internal illumination of the new greenhouse (new shed) is 10%-15% lower than that of natural light. When the shed film has dust or condensation in the film, the illumination in the shed can drop by more than 50%. The recommended way to solve the light is to install a 1000 watt fluorescent lamp in the shed to fill the light. The fluorescent lamp is hung in the middle of the shed. Whether it is to hang two or more rows depends on the width of the shed. The lamp is more than 35 cm from the top of the crop. It is installed every 3-5 meters. Generally, it lights up once in the morning and afternoon. The lighting time depends on the sunlight, to ensure the photosynthesis light demand. . At the same time, there are fewer pests and diseases in greenhouses with sufficient light.
Properly increase carbon dioxide concentration
Under the premise of solving the problem of light, the concentration of carbon dioxide in the shed becomes one of the factors affecting the yield of greenhouse crops. Under normal circumstances, due to crop respiration and soil release before sunrise, the concentration of carbon dioxide in the shed is 2-3 times higher than that outside the shed (300-350ppm). After 8 hours, the photosynthesis can be reduced to less than 100ppm. Therefore, it is recommended to let the wind out after 8 o'clock. One is to supplement carbon dioxide, and the other is to remove harmful gases (such as ammonia, nitrogen dioxide, ethylene, etc.). In the case of weak light and low temperature in winter and spring, the artificial application of carbon dioxide has a significant effect on yield increase.
Adding warming facilities
In winter or early spring, the outside temperature fluctuates greatly. In case of heavy snow or cold current, the crops in the shed often suffer from low temperature damage and poor growth. In the case of special low temperature weather, in order to ensure the base temperature in the shed (the crop is not chilled), the temperature increasing equipment is turned on to prevent the production from being reduced. The main methods are: electric heating line to increase ground temperature, electric heating or furnace heating. Another simple and easy method is to place a water bag (a plastic bag full of water) in the greenhouse. The water is more than the heat. During the day, the water bag absorbs a lot of sunlight energy and converts it into heat energy for storage. Come out to increase the temperature of the shed.
Reasonable adjustment of humidity in the shed
The air humidity in the shed not only affects photosynthesis and absorption of mineral nutrients, but also directly affects the occurrence of pests and diseases. The law of humidity change is: the greenhouse is closed, the exchange of air between the shed and the outside air is blocked, and the moisture of the soil evaporation and transpiration of the leaves is difficult to disperse, so the humidity in the shed is large. If no dehumidification measures are taken, even if the air is ventilated during the day, the relative humidity of the air in the shed is 70%-80%, more than 90% after rainy days or irrigation, and 100% at night (because the relative humidity of the air in the shed will follow The nighttime temperature is lowered and the grass cover is closed and the shed is raised. At this time, the wet air in the shed condenses into a water film or water droplets adheres to the inner surface of the plastic film or the stem of the crop, which is extremely beneficial to the spore germination of the pathogen.
The effective methods of dehumidification are: (1) ventilation and ventilation when the temperature is high and humidity is high; (2) heating in the shed when the temperature is low and humidity is high; (3) using drip irrigation technology to save water and fertilizer; (4) adopting Covering cultivation techniques, ensuring soil temperature, reducing soil moisture evaporation, reducing the number of watering, and greatly reducing the air humidity by about 20%; (5) placing strong water-absorbent materials in the shed.
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