Analysis of the Influence of Temperature and Humidity in Greenhouse on Crops

First, the adjustment of humidity conditions

Due to the evaporation of soil in the greenhouse and the transpiration of vegetables, the humidity in the shed is significantly higher than that in the open field. In terms of the growth and development of vegetables, the appropriate relative air humidity is about 35% during the day and about 83% at night. The relative humidity of the air in the shed is: sunny, windy, relatively low relative humidity, high humidity in cloudy, rainy, and snowy weather; high humidity in the morning and lowest humidity in the afternoon. Under normal circumstances, the humidity in the greenhouse is generally high, which is not conducive to the growth and development of vegetables, and is easy to induce disease. Therefore, the humidity management in the greenhouse should be based on dehumidification. The adjustment measures are:

1, ventilation and humidity

Adjust the humidity conditions in the greenhouse by ventilation. However, the temperature in the greenhouse is also reduced during ventilation and dehumidification. Therefore, the ventilation should be carried out at 9-14 hours, so that the humidity and insulation can be taken into consideration. In the cold winter, it is necessary to use heat preservation to minimize the number of ventilations and time; in spring, the ventilation should be appropriately increased to coordinate the temperature and humidity in the shed to alleviate the contradiction between temperature and humidity in the shed.

2, water control and dehumidification

By reducing the amount and frequency of irrigation, the humidity in the shed can be adjusted. Under the premise of satisfying the water required for the growth and development of vegetables, the number of irrigations should be reduced as much as possible, and the humidity of the soil and air should be reduced. ,

Second, the adjustment of temperature conditions

Vegetable cultivation in greenhouses is mainly in winter and spring, and temperature conditions are the driving force for the growth and development of vegetables. The law of temperature change in the greenhouse is: the temperature difference between day and night is large; the temperature difference between sunny days is greater than that of cloudy days, and the temperature of the shed is rising faster; the effect of temperature increase in cloudy sheds is not obvious. According to the temperature change law in the greenhouse, the following temperature adjustment measures can be taken:

Temperature-increasing measures: multi-layer cover, multi-layer film covering measures, such as sheds in the shed, mulch in the shed; grass curtains to prevent cold. At night, on the inner side of the greenhouse, about 1 meter high straw curtains can generally increase the temperature inside the greenhouse by 1-2 degrees. Or cover the straw curtain on the small shed, there is also obvious warming and heat preservation effect. However, the coverings in greenhouses such as small sheds and straw curtains are generally covered at night and removed during the day to enhance the coverage of the sheds and improve the light utilization rate; the furnace is warmed. In the case of particularly cold weather, you can use the stove set in the shed to quickly increase the temperature inside the shed, but pay attention to prevent vegetable gas poisoning.

Third, the adjustment of lighting conditions

At present, the light in the greenhouse is still dominated by natural light, but the utilization of natural light in the greenhouse is low, generally only 40%-60% of the exposed environment. Therefore, it is necessary to increase the illumination in the greenhouse as much as possible to meet the requirements of the light conditions of vegetable growth and development. In addition, the light directly or indirectly affects the temperature and humidity in the greenhouse and the conditions such as carbon dioxide. In addition to the influence of seasons, weather and other factors, the following factors can be artificially selected and adjusted to meet the requirements of light conditions for vegetable growth and development. The specific adjustment measures are:

1. Appropriate orientation

In the same place, the greenhouses are used in different ways, and the utilization rate of light is also different. Considering various factors, the orientation of the greenhouse should generally be selected from north to south and east and west, and the northern mode can obtain the best lighting conditions.

2, control film age

In the use of shed film, there will be an "aging" phenomenon, which will reduce the light transmission performance of the shed film. For more than three years, the opacity film can reduce the light transmittance by 20%-30%, which seriously affects the lighting conditions in the greenhouse. Therefore, the service life of the shed film is best in 2 years.

3, wash the shed film

The dusty and condensed frost on the greenhouse film can reduce the light in the shed by 10%-20%. Therefore, timely washing of the shed film to prevent condensation on the dust and the film on the shed film is an important measure to prevent the lighting conditions in the shed, especially during the early spring and low temperature.

4, plant growth (fill light) lamp

The plant growth lamp can effectively provide the wavelength of growth light required by the plant.

The wavelength type is rich, which coincides with the spectral range of plant photosynthetic and photomorphogenesis. It can concentrate light of specific wavelength and evenly illuminate crops; it can not only regulate crop flowering and fruiting, but also control plant height and plant nutrient composition; wavelength type It is rich in the spectral range of plant photosynthetics and photomorphogenesis. It has a better effect of light scattering and evenly irradiates crops. The system has less heat and takes up less space. It can be used in multi-layer cultivation stereo system, achieving low heat load and small production space. Environmental protection, energy saving, no harmful gases, no pollution to the environment, high luminous efficiency: 90% of the emitted light can be absorbed by plants, while traditional high-pressure nano lamps and metal halide lamps have only 8-10% light effect; Small, lifespan of up to 8,000 hours; exceptional durability also reduces operating costs.