After entering the summer, as the light becomes stronger and the temperature rises, the temperature in the shed is too high and the light is too strong, which has become the main factor affecting the growth of crops. To reduce the temperature and light intensity in the shed, shading nets are the first choice. However, many farmers recently reported that although the temperature has decreased after using the shade net, the cucumbers have problems of weak growth and low yield. After a detailed understanding, the editor believes that this is caused by the high shading rate of the sunshade net used. There are two main reasons for the high shading rate: one is the problem of the use method; the other is the problem of the sunshade net itself. For the use of sunshade nets, the following aspects should be paid attention to:
First, we must choose the correct sunshade net. The colors of shade nets on the market are mainly black and silver-gray. Black has high shading rate and good cooling effect, but has a greater impact on photosynthesis. It is more suitable for use on shade-loving crops. If used on some light-loving crops. Coverage time should be reduced. Although the silver-gray shade net is not as effective in cooling as the black one, it has less impact on the photosynthesis of crops and can be used on light-loving crops.

Second, use the sunshade net correctly. There are two types of shading net covering methods: full coverage and pavilion-type coverage. In practical applications, pavilion-type coverage is used more because of its better cooling effect due to smooth air circulation. The specific method is: use the skeleton of the arch shed to cover the sunshade net on the top, and leave a ventilation belt of 60-80 cm on it. If covered with a film, the sunshade net cannot be directly covered on the film, and a gap of more than 20 cm should be left to use the wind to cool down. Although covering the sunshade net can reduce the temperature, it also reduces the light intensity, which has an adverse effect on the photosynthesis of crops, so the covering time is also very important, and it should be avoided throughout the day. When the temperature drops to 30 ℃, the shade net can be removed, and it is not covered on cloudy days to minimize the adverse effects on crops.
The survey also found that the problem of the shading net itself is also a factor that cannot be ignored that causes the shading rate to be too high. At present, there are two main types of sunshade nets on the market: one is sold by weight, and the other is sold by area. The nets sold by weight are generally recycled material nets, which are low-quality nets and have a service life of 2 months to 1 year. This net is characterized by thick wire, hard net, roughness, dense mesh, heavy weight, and generally high shading rate. Above 70%, there is no clear packaging. Nets sold by area are generally new material nets, with a service life of 3 to 5 years. This net is characterized by light weight, moderate flexibility, smooth and shiny net surface, and a wide range of shading rate adjustment, which can be made from 30% to 95%. arrive.

When purchasing a shading net, we must first determine how high a shading rate is required for our shed. Under direct sunlight in summer, the light intensity can reach 60,000-100,000 lux. For vegetables, the light saturation point of most vegetables is 30,000-60,000 lux. For example, the light saturation point of pepper is 30,000 lux and eggplant is 40,000 lux. Lux, cucumber is 55,000 lux. Excessive light will have a great impact on the photosynthesis of vegetables, resulting in blocked carbon dioxide absorption, excessive breathing intensity, etc., and the photosynthetic “noon break” phenomenon that occurs under natural conditions is generated in this way. Therefore, the use of shade net covering with suitable shading rate can not only reduce the temperature in the shed before and after noon, but also improve the photosynthetic efficiency of vegetables, killing two birds with one stone.
Taking into account the different lighting needs of crops and the need to control the temperature of the shed, we must choose a shading net with a suitable shading rate. For those with low light saturation points such as peppers, you can choose a shading net with a high shading rate. For example, the shading rate is 50%-70% to ensure that the light intensity in the shed is about 30,000 lux. For cucumbers with a relatively high light saturation point For vegetable species, you should choose a shading net with a low shading rate, such as a shading rate of 35-50%, to ensure that the light intensity in the shed is 50,000 lux.

Article source: Tianbao Agricultural Technology Service Platform

Post time: May-07-2022