How to control the temperature of fruit trees cultivated in greenhouse?

In protected cultivation of fruit trees, temperature is the primary condition affecting the growth and development of fruit trees. In a greenhouse without heating facilities, the heat source mainly depends on solar radiation and ground radiation. The orientation and lighting conditions of the greenhouse have great influence on the temperature in the greenhouse. The temperature in the east-west sunlight greenhouse is generally higher, but the temperature difference in different parts of the greenhouse is larger. The light and temperature in all parts of the north and south greenhouses are consistent. Due to the irradiation of the sun and the adjustment of ventilation and covering measures, the temperature in the shed changes gradually after sunrise, and the highest temperature is around11:00 ~14: 00. After that, it will decrease and reach the lowest point before sunrise the next day, forming a daily temperature difference. The shed has small volume, high temperature during the day, rapid cooling at night, low temperature and large daily temperature difference, which can exceed 25℃; The shed has large volume, small daily temperature difference and relatively stable temperature. According to Hu Ruobing's observation, after the plastic shed was covered with plastic film in mid-February, the average temperature in ten days was above 8℃, which was 4℃ higher than that in the open field. During the 90-day heat preservation period from mid-February to early May, the daily average temperature and total accumulated temperature were 4.965438 0℃ and 437.0℃ higher than those in the open field, respectively. The change of greenhouse ground temperature is similar to that of air temperature, but the highest ground temperature and the lowest ground temperature appear later than the air temperature 1 ~ 2h. The greenhouse temperature should be controlled and adjusted manually according to the requirements of plant growth and development in different phenological periods and the law of temperature change in the greenhouse. The temperature and ground temperature in the greenhouse interact with each other, which has the same important influence on the growth and development of plants.

The adjustment of temperature is mainly divided into three aspects: heating, cooling and anti-freezing. The main measures to improve the greenhouse temperature are: the greenhouse is equipped with heating equipment; Using hot brewing raw materials to raise ground temperature and promote temperature rise. The commonly used raw materials for hot brewing mainly include fresh horse manure and fresh manure, which are applied underground. When it is sunny at noon, the temperature in the greenhouse is often higher than the optimal temperature for plant growth. Especially after entering May, the temperature in the shed is sometimes as high as 30℃ or above at noon, so it must be ventilated to cool down. Ventilation and cooling can be divided into natural ventilation and artificial ventilation. When it rains and is cold at night, the temperature in the shed drops. Cold prevention measures include: covering the shed with grass curtains to prevent cold; During the cold current, according to the temperature change in the shed, hot water can be used for cold protection in the shed, and hot water is put in the shed to prevent cold with hot water steam; Smoke prevents freezing, smoke outside the shed drives away cold and increases frost, and slows down the temperature drop inside the shed.