How to reduce the humidity of vegetable greenhouse with too much humidity

Greenhouse vegetables

Due to various reasons, it will cause excessive humidity in the shed, condense a large number of water droplets on the film, vibrate the arch or film slightly, and it will be like a light rain in the shed. This will not only affect the light transmittance of the film, but also cause the prevalence of some diseases (such as downy mildew, Botrytis cinerea, blight, etc.), thus affecting the growth of vegetables.

Cause

There is too much rain and snow in front of the shed. Before covering the plastic film, there is more rain and snow or more soil water content in the greenhouse. After covering the film, the temperature of the greenhouse is too high and the soil water evaporates too much, which will cause too much humidity in the greenhouse.

It's not watered properly. After vegetable planting or flooding irrigation after planting, the amount of water is too large, or more times of watering will lead to large soil water content and increase the humidity in the greenhouse.

Open canals carry water. If the irrigation water is transported by open channels and enters the shed, each watering will cause too much humidity in the shed due to too much water content in the ditch.

The location is inappropriate. When building the shed, the selected location is inappropriate, the groundwater level is high, the terrain is low-lying, and the drainage is not good, resulting in the increase of humidity in the shed.

The lookout is not timely. The main function of greenhouse ventilation is to cool down and dehumidify, especially when there is more soil water content, it is more necessary to release air and dehumidification in time, if the ventilation is not good, a large number of water droplets will be condensed on the film, thus increasing the air humidity in the greenhouse.

Greenhouse vegetables

Solution.

1. Covering the non-drip film with the drip-free film can significantly reduce the humidity, and the light transmittance is good, which is 10% higher than that of the general agricultural film, which is conducive to increasing temperature and reducing humidity.

2. Ventilation, dehumidification and ventilation should generally be carried out around noon when the temperature is high, mainly to put the head wind and waist wind, not the foot wind, in order to prevent the greenhouse temperature is too low and "sweep wind" injury seedlings. In the depths of winter and early spring, it is not appropriate to release early wind and dehumidification. The high temperature season should be ventilated early, gale, and closed late, even if it is cloudy, it should be ventilated for a short time when the outdoor temperature is high at noon. If the humidity in the shed remains high, the ventilation volume should be gradually increased to make the air humidity drop as soon as possible, but the cooling caused by ventilation should be based on the premise that there is no chilling injury to the crops.

3. Plastic film mulching can reduce soil water evaporation and irrigation times, which is an important measure to reduce air humidity in greenhouse. For example, in the shed, large and small ridges are used alternately, and the plastic film covers double ridges, and when watering, water flows into the small ridges under the plastic film.

4. Reasonable watering is the main factor leading to the increase of humidity in the greenhouse. The frequency of watering and the amount of water each time should be watered according to the weather, soil conditions, types of vegetables, growth period and growth potential, generally should be irrigated with small water or ditch rotation, and must not be irrigated by heavy water or flooding. If vegetables, planting water and slow seedling water should be watered thoroughly, adequate water supply should be provided in the fruiting period, and generally no watering is needed in other periods. When the temperature in the shed is low, especially when it can not be ventilated, watering should be controlled as far as possible, let alone border irrigation. Watering should be from 10 to 12:00 on sunny days, and should be ventilated and drained. Do not water in the afternoon, cloudy days and rainy days. Avoid continuous rainy days after watering. When there are conditions, furrow irrigation or drip irrigation under plastic film can be used to reduce irrigation and evaporation.

5. Thermal insulation materials with good moisture absorption and good moisture absorption, such as non-woven cloth, can prevent condensation on the inner surface and prevent dew from falling on the plant, thus reducing air humidity and crop wetting.

6. When the indoor temperature increases by 1 ℃, the relative humidity in the air decreases by 3%. The method of heating up and reducing humidity can not only meet the temperature needs of vegetables, but also reduce the air relative humidity. When the plant grows to have resistance, the temperature of watering closed shed lasts for about 30 ℃ for about 1 hour, and then ventilation and dehumidification. 3When the greenhouse temperature is lower than 25 ℃ after 4 hours, it can be repeated again.

7. The air humidity in the greenhouse of dust method and smoke method is already very high, and the humidity should be increased by using conventional spraying method, which is disadvantageous to the prevention and control of diseases. The use of dust method and smoke method can avoid increasing air humidity due to spray and improve the effect of prevention and control.

8. Wet utilization in ploughing and dispersing. When the temperature of the greenhouse in sunny day is high, hoe the surface shallowly to speed up the evaporation of topsoil water. At the same time, the pores of the soil are cut off to prevent the deep water from moving upward.

9. Hanging the reflective screen can not only increase the light intensity, but also increase the ground temperature by about 2 ℃. Because the relative humidity decreases with the increase of temperature, so hanging reflective screen also has a certain humidity-reducing effect.

10. Natural moisture absorption can use materials such as rice straw, wheat straw and quicklime to absorb water vapor or fog between rows to achieve the purpose of reducing humidity.