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Greenhouse is one of the most widely used production methods in agricultural production . It is widely used because of its advantages such as less weather impact, strong artificial controllability, and high yield. However, because the concept of various data control in the greenhouse is not perfect, the monitoring and intelligent system of the greenhouse is particularly important. The proposed intelligent control system for the greenhouse is to help the greenhouse growers better and more manage the greenhouse. The greenhouse intelligent control system can automatically control a series of parameters such as temperature and humidity , light intensity, air content, soil moisture and nutrients in the greenhouse. How to achieve intelligent control of temperature and humidity during the production process in a greenhouse?
The greenhouse has strong airtightness and is impervious to water. In a closed state, the temperature and humidity of the air in the greenhouse is often 80% to 90%. The change rule of air temperature and humidity in the shed is: the shed temperature increases, the relative temperature and humidity decrease, the shed temperature decreases, and the relative temperature and humidity rise; the relative temperature and humidity decrease in sunny and windy days, and the relative temperature and humidity in rainy weather increase significantly. In spring, with the rapid rise of shed temperature every day after sunrise, plant transpiration and soil evaporation intensify. If not ventilated, the water vapor volume (absolute dui temperature and humidity) in the shed will increase a lot, and the temperature and humidity in the shed will drop after ventilation until the afternoon. Before closing the wind, the temperature and humidity dropped to a low point. At night, when the temperature drops, the shed film will condense a lot of water droplets, and the relative temperature and humidity reach a saturated state.
When the relative temperature and humidity in the shed reaches a saturated state, increasing the shed temperature can reduce the temperature and humidity. Relevant tests show that when the shed temperature is 5 to 10 ° C, the relative temperature and humidity can decrease by 3% to 4% for every 1 ° C increase; if the shed temperature reaches 20 ° C, the relative temperature and humidity is 70% to 75%. So what should we do to maintain the temperature and humidity values in the greenhouse production process?
1. No drip film:
The use of non-drip film can reduce the amount of water accumulated on the film surface, overcome the disadvantages of a large number of water droplets attached to the film, significantly reduce the temperature and humidity, and have good light transmission performance, which is also conducive to temperature increase; spray drops on ordinary film surfaces, or periodically Spraying milk powder, soy flour, etc. on the film surface can also reduce the amount of water accumulated on the film surface.
2. Ridge cultivation:
The high ridge has a large surface area, receives more light during the day, and absorbs more heat from the air. Therefore, the temperature rises faster, the soil moisture evaporates faster, and the temperature and humidity are not easily high.
3. Cover the mulch:
Covering the mulch film can greatly reduce the evaporation of ground moisture and reduce the number of irrigations, thereby reducing the air temperature and humidity. At the same time, the ground temperature at 10cm can be raised by 2 to 3 ° C on average. Width, cover the cultivation area, gutters, etc. in the shed with plastic film.
Ventilation is the most basic method of dehumidifying plastic greenhouses. When constructing a greenhouse, design ventilation doors and ventilation walls, and add vents in the middle of the greenhouse to increase communication with outdoor air. Design to ensure that the film can be buckled to block the insect screen when necessary. For multi-arch sheds, skylights should be designed to increase ventilation. Within 1d, the time of good ventilation and dehumidification effect is noon, because the temperature and humidity inside and outside the shed during this period are greatly different, and the humidity is relatively easy to discharge; in other periods, the ventilation time should be extended as much as possible under the premise of ensuring the temperature requirements. In addition, special attention should be paid to strengthening ventilation and dehumidification in the greenhouse 2 to 3 days after watering, 1 to 2 days after foliar spraying (medicine), rainy (snow) days, and before and after sunset.
5. Improve the fang method:
When it is necessary to apply medicine in the shed, use the dust method and the smoke method. If spraying method is used, it must be done in the morning on a sunny day, so that there is enough time to ventilate and dehumidify after spraying.
6. Water control and dehumidification:
By reducing the amount and frequency of irrigation, the temperature and humidity in the shed can be adjusted. On the premise of satisfying the moisture required for the growth and development of vegetables , the number of irrigations should be reduced as much as possible, and the temperature and humidity of the soil and air should be reduced, so as to be dry and not wet. Watering should be "five watering and five watering": watering on sunny days and no watering on cloudy days; watering in the morning and no watering in the afternoon; pouring small water and not flooding; low water temperature in winter. Preheat in the shed, and pour it when the water temperature is close to the ground temperature; At the same time, we must vigorously promote new irrigation technologies such as drip irrigation and sub-film irrigation.
7. Cultivated loose soil:
When the temperature of the shed is high on a sunny day, the ditch and the ridge back should be cultivated in time, the capillaries should be cut off, the dry and wet on the plow layer should be prevented, the lower layer of soil water should be prevented from moving to the top soil, and the surface moisture should be reduced to reduce the temperature and humidity in the shed.
8, high temperature dehumidification:
In the morning, don't let out the wind, and the temperature should be increased as much as possible without harming the cultivated crops. As temperature rises, temperature and humidity gradually decrease. When the temperature rises to the peak value of the suitable temperature for the cultivated crops, the wind is released.
9. Artificial moisture absorption:
If the temperature and humidity in the shed are too high, hang or lay materials with good hygroscopicity in the facility, such as quick lime, straw, wheat straw, plant ash or fine dry soil, to absorb the moisture in the air and prevent the air temperature and humidity from becoming too high. To achieve the purpose of natural moisture absorption.
May 15, 2017
Chengdu Xinxin Electronic Technology Co., Ltd. Editorial Department
Editor: Little Devil in Gourd