Talking about the Ventilation Management of Energy-saving Sunlight Greenhouse
Energy-saving solar greenhouses use solar energy as the main source of heat, and do not warm the temperature or make only a small amount of temperature during the winter to complete the annual production of vegetables. Because of its low operating costs and quick results, the development of a large area in the north during the 1990s brought significant benefits to local farmers. However, in the environmental management of greenhouses, there are many problems in the methods and methods of ventilation, which cause great losses to the production of greenhouses. The purpose of this paper is to explore the correct ventilation methods and methods for energy-efficient solar greenhouses so as to guide production. First, the role of ventilation 1, cooling. The main function of ventilation is to reduce the indoor temperature by means of wind pressure or hot pressure in order to meet the required temperature for the growth and development of vegetables. 2, humidity. Due to the relatively closed environment of the facilities, the indoor humidity is generally high, which affects the normal growth of crops and is conducive to the occurrence of some diseases. Ventilation can effectively reduce the humidity in the greenhouse. 3, eliminate harmful gases. Due to improper fertilization, unscientific heating and heating, or the quality of the film, it is easy to produce harmful gases such as NH3, NO2, CO, SO2, C2H4, HF, etc. If the ventilation is not timely, it will cause harm to the vegetables. 4, supplement carbon dioxide. Ventilation into fresh air, to a certain extent, can make up for the lack of CO2 in the greenhouse, and promote the photosynthesis of vegetables. Second, ventilation methods and effects 1, the top ventilation. The top film is quilted or vented at the rear slope, ventilated by hot press. Because the tuyere is far away from the vegetables, the cold air does not blow directly to the plants and generally does not subject the vegetables to cold or freezing injury. Ventilation is less affected by outside air temperature and crop growth periods, and has the best effect. 2. Ventilation of the front roof. Its vents are located at the seams of 80-100cm high skirts and membranes, where they are quilted and vented. This vent has a low position and poor heat dissipation. It is used in conjunction with the top ventilation. When ventilation is used in this way, cold air can easily injure the plants, so it can only be used when the outside air temperature is slightly higher and the top ventilation is not lower than the temperature. 3, the rear wall ventilation. Ventilation windows are left on the back wall about 1m away from the ground. Because the vents are facing the upper part of the plant, when the external cold air is blown in, the young plants are extremely prone to frostbite. This ventilated air was mostly exposed to the outside temperature at the back of the greenhouse in early summer. Use to help cool the top and front roof. 4, foot ventilation. The shed film is designed as a whole and the front foot is not fixed. The purpose of ventilation through the hanging of the film at the front foot is poor ventilation, and it is basically not used at present. Third, the problems in the ventilation management 1. There is very little top ventilation, and the design and construction of greenhouses and the evacuation of sheds at the top are rarely reserved. In production management, only the front roof and the rear wall are used for ventilation. In this way, when the outside temperature is low in winter, late autumn and early spring, the cool air blows directly to the growing point of the plant, and it is easy for the crop to be frozen and chilled. The situation of high indoor temperature but inconvenient ventilation is formed; on the other hand, in high temperature season, the high temperature at the top of the greenhouse leads to poor crop growth, which means that the best ventilation method is not well applied in production. 2, there is the application of ventilation at the bottom. With the ventilation at the bottom, cold air is blown directly from the roots, commonly known as "sweeping the wind", without any buffer, which is very unfavorable to production. Especially in the nursery, seedling stage and planting period, the adoption of this ventilation method will seriously affect the survival of the seedlings. 3, vent switch period, improper size. Whenever the size of the switch and vents are adjusted, there is no theoretical basis and only the experience and feelings. Sometimes the size of vents is constant from open to closed, which will inevitably cause the indoor temperature to rise and fall, that is, the temperature is too high or too low, which is unfavorable for the growth and development of vegetables. 4, improper use of ventilation. There is no theoretical basis for which or several types of ventilation methods and the application of various ventilation methods are used. It is only based on experience or convenience. This results in poor ventilation and can easily harm crops. 5, the purpose of ventilation is not comprehensive. Focusing only on cooling, ignoring the effects of dehumidification, detoxification, and carbon dioxide supplementation, especially in the morning, these disadvantages have become more prominent. Fourth, solve the countermeasures 1. When the new greenhouse is designed or constructed, it must be provided with vents or a pull-out tube on the backslope. Or when the film is buckled, a quilting opening is provided at the top to achieve ventilation at the top. 2, according to the changes in the temperature of the greenhouse in a timely manner to adjust the ventilation switch and size, to avoid dramatic changes in temperature, or high, low. Normally when the temperature rises to 28°C (winter) or 25°C (spring, autumn). In general, the temperature of vegetables began to be ventilated, and the size of the vents was gradually increased after the temperature was not lowered. With the increase of light, the temperature increased further and the vents gradually increased. The maximum temperature before and after noon should not exceed 32°C. In the afternoon, when the temperature drops to 25-28°C, the ventilation openings should be gradually closed. When the temperature drops to 20°C, the ventilation openings should be closed. 3, in the use of several ventilation methods, the correct order is to open the top vents, when the temperature is still rising, then open the front vents, vents on the back wall. When closing the vents, the opening is reversed. The vents on the rear wall are closed, the vents on the front are closed, and the vents on the top are closed. 4. At the same time (or after watering), basically meet the vegetable's demand for temperature at the same time, open the vents in a timely manner and conduct dehumidification, detoxification, and carbon dioxide supplementation to achieve the full effect of ventilation. Chunmee Green Tea,Chunmee Green,Loose Green Tea,Osk Green Tea Hunan Junshan Yinzhen Tea Industry Co.,Ltd , https://www.junshan-tea.com