At present, greenhouse production is still a trend of development. However, in the end, what type of greenhouse is needed to ensure that vegetables do not suffer from cold damage. After years of research, experts believe that the following aspects must be taken into account when building greenhouses.
Increase wall thickness and back slope thickness to enhance greenhouse insulation performance
The regenerative surface of the greenhouse includes three walls, a back slope and the ground. When the vegetable plant is covered with a hard surface, the wall and backslope become the main heating surface. The requirement to increase the thickness of the wall and back slope is mainly to increase its heat storage capacity, and of course it does not exclude the effect of its cold insulation. Among them, whether or not thermal insulation can be the key to the success of winter greenhouse production. Practice has proved that in order to resist severe weather in winter, the width of greenhouse walls should reach 2 meters and the width should reach 1.5 meters, which is a trapezoid. If building a brick wall, the thickness should not be less than 1.2 meters, that is, 50 centimeters inside the heat absorption layer, hollow 80 centimeters, filled with bundles of wheat straw, as a heat insulation layer, 18 centimeters outside as a cold layer. Outside the wall in winter, corn stalks of 30 cm thickness should be used again.
Build a semi-submerged surface for better soil temperature
If the earth wall greenhouse is built, some of the soil on the south side of the wall can be pushed onto the wall, and the wall can be compacted with a bulldozer, and then the inner wall can be straightened and straightened. Because there are more soils in the wall, the indoor surface is 30-40 cm lower than the outdoor surface.
Although there is a little shading on the south side of the semi-underground surface, the indoor surface is lower than the outside, and the soil temperature in the room will not be reduced too quickly, which can play a good role in insulation. This is one of the reasons why the low-lying cultivation in winter greenhouses can increase production and increase income.
Increase slope thickness to avoid uneven thickness
The rear slope of the greenhouse is facing north, and is the main cooling surface like the wall. Therefore, when building a backslope, its elevation angle should be around 45 degrees. The high elevation makes the backslope an ideal light-receiving surface. With a small elevation angle, not only is it difficult to receive light and heat, but it also blocks the rear wall and affects the light and heat storage of the wall.
The thickness of the rear roof should be in the range of 50-60 cm. At present, the slope of most greenhouses is thick in the north and thin in the south. Some of the southern slopes of the roof are only 10 to 15 centimeters thick. This issue must be taken seriously.
Increase span and length to increase available area
The greenhouse is a high-input facility. On the basis of the original, a little more investment can increase the indoor area. According to the calculations, if the greenhouse extends 1 meter to the south, the available area will increase by 11%, and the ridge height will only increase by 20 centimeters to reach the ideal roof angle. Increasing the length of the greenhouse is also a way to reduce input and expand the area planted. More importantly, after the increase in indoor space, the temperature changes smoothly, especially at night when the cooling rate is slow. Therefore, with the length of the plot allowed, the greenhouse, which is currently 50 meters long, can be lengthened to 100 meters or even longer.
Protect the front roof
The front roof of the greenhouse (film coverage) is the light-receiving surface during the day (requires daily cleaning and maintains good light transmission), and is the largest heat-dissipation surface at night. Because its surface area is equal to the indoor land area, if such a large heat-dissipating surface is not well protected, the heat storage of the wall and the back slope will be even worse. At present, people use grass cover to protect the front roof. The thickness of the grasshopper is more than 5 cm. When the cover is to be pressed before the press, the pressure at the connection is not less than 20 centimeters, and the cover should be covered with a waterproof insulation film to prevent the snow and dew from wetting the grass and reduce the insulation. It has been determined that the temperature of greenhouses covered with grasshoppers can be increased by about 1.5°C compared to the greenhouses without rainproof membranes.
Practice has proved that as long as we can build a greenhouse according to the above, and then protect the front roof, with new varieties, new technologies, planting cucumber, per mu can exceed 15,000 kilograms, planting tomatoes, per mu can exceed 10,000 kilograms.
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