Spring is the most intense season for air convection during the year. The cold air in the north gradually recedes. The warm and humid air in the southwest and southeast gradually strengthens. It is the strongest wind season in the year. In the spring, strong winds are common, and greenhouses and sheds are easily damaged. Vegetable farmers must do a good job of preventing winds.
I. Greenhouse Safety Wind Management
Watching the weather forecast in a timely manner and adopting appropriate countermeasures according to the forecasted wind force are the basis for preventing the danger of strong winds. In general, when the wind power is above level 5, it is necessary to consider the windproof work of the shelter. In order to predict the magnitude and direction of the wind force, the roof covering is compacted in advance. When the storm hits, the biggest threat is to scrape or scrape the floating membrane and scratch the straw curtain, which affects the temperature in the shed. Secondly, if there is precipitation, it will affect the next day to pull the straw curtain. So how does a vegetable farmer ensure that the cover is not affected by strong winds?
1. According to the wind pressure floating membrane
Below the 5th level, the north wind does not pose much threat to the straw curtain, but the westerly wind or the easterly wind can blow the straw curtain. In order to prevent the straw curtain from being blown over after putting it down, the main measure is to cover the floating membrane. When the shed is put in the evening, if the wind is blowing on the westerly wind or the westerly wind, for the floating membrane fixed on the back slope of the shed, the vegetable grower can press and fix the west side of the floating membrane, so that the wind will not blow into the bottom of the floating membrane. It can also press the air formed in the airbag when the film is floated to press it out, so that the float film can be tightly attached to the straw curtain to prevent the strong wind from blowing up the floating film and blowing the straw curtain. When the wind is blowing in the east wind or the east wind, it also adopts the same Laminating method. For a fixed floating film, special attention must be paid to the north side of the floating film.
2. Adjust the time to pull the straw curtain
During the day, many winds start to rise in the morning and gradually increase, and the winds will decrease in the evening. Therefore, windy weather farmers can pull sheds early and put them in the shed. The vegetable grower can advance the pulling time to 7:00 am (afterwards, with the weather warming, the sunshine duration is extended, and the pulling time should be gradually advanced). At this time, the general wind power is relatively small and will not affect the straw curtain. By the afternoon, the wind gradually decreased, and farmers could postpone the time until after 5 o'clock. For old straw curtains used for many years, in order to prevent high winds from blowing the straw curtains, many vegetable farmers can put them together to shorten the shelf time and reduce the chance that the straw curtain will be blown by the wind. It should be noted that the vegetable farmer should properly adjust the time for closing the vents to avoid excessive temperature drop in the shed.
Second, arch shelter safety wind management
1. Set more film rope when there is a tall object on the shed
According to many years of experience, if there are tall objects such as houses, trees, etc. near the arch shed, strong winds will cause cyclones or turbulence due to the obstruction of these objects, especially when these objects are in the south direction of the arch, the swirling airflow After being blocked, it descends and enters the shed through more entrances and exits on the south side of the shed, causing inconsistent air pressure in the shed, which may cause the shed film to burst. If there are tall objects near the proposed shed, the vegetable grower should increase the number of membrane ropes and close the entrance and exit of the arch shed to prevent the air flow from entering.
2. Arch shelters with small shed face angle and high sides should strengthen wind protection work
If the ventilation shed is not strict, the air pressure through the shed can easily cause different pressures inside and outside the shed, and the shed film can be blown up and down. The shed film can be broken and it may seriously lead to the entire shed. Collapse. Therefore, such a shed must take the following measures:
(1) Renovation of the arch structure, reducing the height of the columns on both sides, strengthening the bearing capacity of the columns on both sides, and increasing the arch of the shed.
(2) Increase the number of film ropes on the sheds and close the vents to improve the wind resistance of the shed body.
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