The weather turns cold, and Agricultural University is going to replace the greenhouse film. What problems should be paid attention to when replacing greenhouse film?

Beginning in late September, it entered the peak period of film changing in greenhouses. Especially in the first half of the year, when some vegetable farmers' greenhouse membranes are damaged, they are often replaced in advance. After one year's use, the light transmittance of the old shed film decreased greatly, generally only 60%-70%. After autumn, although the temperature drops rapidly, there are many sunny days and strong sunshine during the day. After replacing the new shed film, the light transmittance of the new film is above 90%. Changes in environmental conditions will inevitably lead to great changes in pests and diseases. Vegetable farmers should pay attention to strengthening management to reduce the probability of problems. (a) to prevent flash off. Before changing the film, it is necessary to expand the vent and strengthen the ventilation, so that the temperature inside the shed is as consistent as possible with the temperature outside the shed. This is very important, because the temperature and humidity inside the shed are often higher than outside.

If the film is replaced directly without ventilation, it is easy to cause "flash shed" (2) film replacement time. The shorter the film changing time, the better. The shorter the film changing time and the longer the dragging time, the greater the influence of external environment on greenhouse vegetables, which is not conducive to the growth of vegetables. (3) Choose sunny days. When replacing the greenhouse film, choose sunny weather, because it has the least adverse effect on vegetables. When we choose the right weather, we must choose the time to change the film. It is most suitable to change the shed film when the outdoor temperature is high at noon. At the same time, pay attention to the wind direction before changing the film. If the wind is too strong, don't change the film first, so as not to blow it off when changing the film. (4) pest control.

After replacing the plastic film in the greenhouse, it should be sprayed and disinfected immediately. During the film changing process, various pests and pathogenic spores may enter the shed. Therefore, pesticides should be sprayed immediately after replacing the new membrane to prevent insects and sterilize. The bactericide can be selected from chlorothalonil, metoprolol and other bactericides. Insecticidal bacteria can use imidacloprid and chlorpheniramine, which can kill most pests. Replacement method of greenhouse film. Under normal circumstances, many farmers grow vegetables first, and then change the greenhouse film. However, in the process of replacing the greenhouse film, it is easy to have problems that affect the growth of vegetables. After mastering the above four points, you can change the shed film more safely.