https://www.greenhousevendor.comThe construction of greenhouses should strictly control the air humidity
Greenhouses are widely used for the cultivation and production of vegetables, and with the improvement of people's living standards, the demand for off-season vegetables also increases. As the hardware of the "vegetable basket" project, greenhouses are gradually standardized from creation to environmental control. Here, the editor will introduce to you why it is necessary to strictly control the air humidity in the construction of greenhouses, and how to control the humidity?
1. The rules for changing the air humidity in the greenhouse: the plastic film has a strong seal, the air in the greenhouse is blocked from communicating with the outside air, and the moisture from soil transpiration and leaf transpiration is difficult to dissipate. Therefore, the humidity in the shed is high. During the day, under the condition of ventilation in the greenhouse, the relative humidity of the air in the greenhouse is 70-80%. It can reach more than 90% in cloudy and rainy days or after irrigation. The relative humidity of the air in the shed decreases with the increase of temperature. When the humid air in the shed is cooled, it condenses into a water film or water droplets attached to the inner and outer surfaces of the film or on the plants.
2. Control of air humidity: Excessive air humidity in the greenhouse not only directly affects the photosynthesis of vegetables and the absorption of mineral nutrients, but also facilitates the germination and infection of bacterial spores. Therefore, ventilation should be carried out to promote the exchange of the high-humidity air in the shed with the low-humidity air outside, which can effectively reduce the relative humidity in the shed. The heating inside the shed can also reduce the relative humidity. The use of drip irrigation technology, combined with plastic film mulching, reduces soil water transpiration and can greatly reduce air humidity.
High temperature and high humidity or low temperature and high humidity in the greenhouse can easily cause the outbreak and extension of pests and diseases. Therefore, it is necessary to adopt reasonable irrigation methods to regulate and control, so as to facilitate the stable and high yield of vegetables.
Ventilation and moisture removal After each irrigation, it is necessary to adjust measures according to the situation. On the premise of ensuring that the temperature is not affected, increase the ventilation amount, discharge the moisture out of the shed in time, and then reduce the humidity in the shed. Especially on sunny days, the temperature in the solar greenhouse is high. If there is no ventilation after irrigation, not only will the humidity be added, but the plants will easily grow leggy. The size of ventilation should be controlled according to the temperature. It is ventilated when it is higher than 30 °C, closed when it is lower than 20 °C, and the temperature is kept at 28-30 °C.
Deep ditch and high border Select plots with high dry terrain and convenient drainage to build solar greenhouses. During land preparation, drainage ditches must be dug around the solar greenhouse, and the cultivation method of deep ditch and high border should be adopted in the shed, and the height of the border should be more than 20cm, so as to filter water and stains.
Anti-fogging agent is added to the drip-free film. When the temperature of the film surface begins to drop, the moisture in the air can only condense into a thin water film on the surface of the film. When the water film thickens to a certain extent When the thickness is thick, it flows along the surface of the film to the ground and penetrates into the ground. There is no dew on the lower surface of the drip-free film, which can overcome the drawbacks of many water droplets attached to the inside of the film, and the air humidity in the greenhouse has decreased. It avoids the reflection of dew on sunlight and energy consumption by absorbing transpiration, improving the light transmittance of agricultural film, which is beneficial to the temperature increase and humidity reduction of the greenhouse.
Drip irrigation under film Drip irrigation under film combines the advantages of plastic film covering and drip irrigation, and is an effective way to reduce the humidity in greenhouses. The method is to raise a high ridge on the ground, then put a drip irrigation pipe in the center of the high ridge, and then cover the mulch. The use of drip irrigation in the solar greenhouse can avoid soil compaction and ground temperature drop, and can effectively avoid the significant increase in air humidity caused by watering. And it can reduce the number of irrigation, and then reduce the air humidity.
Hanging the reflective curtain Hanging the reflective curtain can improve the temperature of the ground and the temperature. Because the relative humidity decreases with the rise of the temperature, the hanging reflective curtain also has a certain dehumidification effect.
Application method The application method should be changed from spraying to a combination of fumigation, mist mist, and powder spraying. It should be noted that the general fumigation time should not exceed 8 hours, and the ventilation should be timely after fumigation, so as to discharge harmful gases in the shed and avoid phytotoxicity. In addition, when the powder is sprayed, the powder particles are scattered from top to bottom, which will form a lot of powder attached to the front of the leaf, which will affect the photosynthetic effect.
Artificial moisture absorption If the humidity in the greenhouse is too high, some straw, wheat straw, grass ash or fine dry soil can be sprinkled between the rows, and hygroscopic materials such as quicklime can also be accumulated in the spare part of the greenhouse. After a period of time, choose a sunny day to move straw, wheat straw, quicklime, etc. to the outside of the greenhouse for exposure, and use it repeatedly.
