What kinds of plastic greenhouses are commonly used for watermelon planting?

(1) The plastic greenhouse with reinforced skeleton is a greenhouse assembled by double-layer galvanized thin-walled steel pipe prefabricated parts. There are no columns in the shed, and the shed membrane is fixed by film pressing groove and wire clamping, which is convenient to install, easy to move and durable. Because there are no columns in the shed, the light is good and the operation is convenient. Because of the use of groove-type shed-pressing membrane, the shed-fastening operation is quick and simple, with strong wind resistance and not easy to damage the shed membrane. The disadvantage is that the one-time investment is large, and each shed needs 1 ten thousand yuan. However, if the depreciation is calculated according to the service life of more than 10 years, the annual cost of scaffolding is similar to that of ordinary simple greenhouses. This kind of greenhouse has been widely used in southern and coastal areas with good economic conditions, but it has not been popularized in most melon producing areas. (2) The house-type simple plastic greenhouse is mainly composed of two parts: a bracket and a shed membrane. Generally, the shed width is 12m, the shed length is 40 ~ 50m, the shed height is 2 ~ 2.4m, and the shoulder height is about1.4m. The pillars of the arch are mostly wooden stakes or cement columns with a cross section of 6 cm× 8 cm. Set a row of columns every 3 meters in the east-west direction, and there are 5 rows of columns in total; There is a row of columns every 2 meters in the north-south direction, with about 20 ~ 25 rows of columns. The middle row of columns in the east-west direction is about 2 meters high, the two rows of columns outward are about 1.7 meters high, and the two rows of lateral columns outward are about 1.3 meters high. The beam is made of 6 ~ 8 cm thick bamboo pole, which is fixed at the top of the column, and steel bars can also be used instead of bamboo pole. The upright posts are connected and fixed into a whole by iron wires, and both ends are screwed and fixed on the upright posts. After the greenhouse frame is completed, cover it tightly with several sheets of agricultural film in the north-south direction, press a 6-8 cm thick bamboo pole on the agricultural film outside the greenhouse between the two columns instead of the film pressing line to press the agricultural film tightly, and seal the agricultural film around the greenhouse with soil. (3) simple shed with few columns, commonly known as "bread shed"

The shed span is 6 ~ 8m, and the shed height is 1.6 ~ 2m. Bamboo poles with a thickness of 4 ~ 6cm are directly bent into a semicircle arch, and both sides are fixed underground. Several pillars are planted in the middle of the shed (one pillar can be planted under each row of bamboo poles in windy places), and the upper ends are connected and fixed with iron wires or longitudinal beams, and the spacing between bamboo poles is about 0.8m. Several arches are connected and fixed by longitudinal beams, forming a simple shed with few columns. After the scaffolding is completed, the top outside the shed is covered with 7-9 meters wide agricultural film, and both sides are covered with 1- 1.5 meters wide agricultural film, which is convenient for ventilation. A film pressing line is fixed between the two rows of bamboo poles. The investment per 667m2 greenhouse is nearly 2,000 yuan. Because of its narrow span and small space, the scaffolding is easily affected by the external environment temperature, but it is simple in structure and convenient to build, and is often used in some new melon areas or backward areas. (4) The span of less column cement shed is 6-8m, and the shed height is 2.5-3m. The arched frame is formed by butting two arched reinforced concrete columns with a thickness of about 4cm, with a spacing of about 1.0m, and both sides are fixed underground. A row of columns (one for 3-5 arches) are planted in the middle of the shed, and 3-5 steel pipes are used at the top and both sides. The investment per 667 m2 greenhouse is nearly 6,000 yuan, and the annual cost is equivalent to 1000 yuan, which is much lower than that of bamboo shed, but the strength and effect of shed are much higher than that of bamboo shed, which is economical and practical and suitable for some old melon farmers.