What can be done to prevent the generation of harmful gases in smart greenhouses

Any factor may cause harmful gases in the intelligent greenhouse, endanger the normal growth and development of crops, and even cause crops to wither and die. How to prevent harmful gases from being produced in the intelligent greenhouse and ensure the healthy growth of crops has become the focus of farmers' attention. Here are some feasible solutions for everyone.

Types and hazards of 1. harmful gases

1. Ammonia and nitrous acid gas mainly come from nitrogen fertilizer and organic fertilizer applied to the soil. Especially in the case of excessive fertilization and soil drought, the fertilizer will decompose and produce a large amount of ammonia in a short period of time when it encounters high temperature in the shed. When the concentration of ammonia exceeds 5ppm, some sensitive vegetables, such as cucumbers and tomatoes, will be damaged. The first leaves will turn brown after drying as if they were scalded by boiling water. When the concentration of ammonia reaches 4%, vegetable seedlings will die after 24 hours. When the content of nitrous acid gas in the air reaches 2-3ppm, sensitive vegetables such as eggplant, tomato and pepper will suffer. Its symptoms mainly occur on leaves close to the ground and seldom harm new leaves. At first, it is like being scalded by boiling water. Later, due to the acidification of nitrous acid, the veins gradually become white. In severe cases, only the veins are left, and the mesophyll bleaches and dies.

2. When the carbon monoxide and sulfur dioxide gas plastic greenhouse is heated by coal fire, a large amount of carbon monoxide and sulfur dioxide gas is often produced due to incomplete combustion or unobstructed flue. The hazards of these two gases can be divided into three types: first, recessive poisoning, the vegetables themselves have no obvious damage, but the assimilation function is reduced, the quality is poor, and generally has little effect on the yield; Second, chronic poisoning, gas invades from the stomata on the back of the leaf, causing brown spots and yellowing on the surface of the stomata. Third, acute poisoning produces albino symptoms similar to nitrous acid gas.

3. Toxic gases emitted by the plastic film itself Some plastic films will produce some volatile substances, such as ethylene, chlorine, etc., during use, and can invade the plant through the stomata or water holes on the leaves, destroying cell tissues and chloroplasts., So that photosynthesis is significantly weakened, seriously affecting the yield and quality of vegetables. Some data show that the concentration of chlorine in the air reaches 0.1ppm, radish can be harmed by contact for 2 hours, and the concentration reaches 0.5-0.8ppm. Most vegetables can be harmed by contact for only 4 hours. At the beginning, white or light brown irregular dot or block spots appear between the veins of leaves, and in severe cases, the whole leaves turn white or even fall off. When the concentration of ethylene gas in the protected area reaches more than 1ppm, can make vegetables yellow between the leaf margins and veins, and then turn white until they die. According to the experimental observation, ethylene can also make a variety of vegetable leaves drooping, and has an inhibitory effect on tomato seedlings; in the concentration range of 0.1-3ppm, tomato, eggplant, etc. will appear flowers, buds, young fruits and leaves of abnormal shedding.

2. prevention and control measures

The harmful gas in the greenhouse not only affects the growth and development of vegetables, but also directly endangers the health of vegetable farmers. Therefore, we must take measures to prevent and control.

1. Scientific fertilization of greenhouse vegetables should be based on high-quality soil fertilizer, appropriate application of phosphorus and potassium fertilizer, appropriate application of less nitrogen fertilizer, and adhere to the main base fertilizer, supplemented by top dressing. Topdressing should be strictly in accordance with the principle of "a small number of times" to prevent excessive fertilization. The top dressing method adopts ditching and deep application, followed by covering with soil and watering in time to dilute the fertilizer.

2, timely ventilation use at noon when the temperature is high, open the vent, so that the air circulation; even in cloudy or snowy days, but also at noon for a short period of ventilation, in order to minimize the harmful gases in the shed, reduce air humidity.

3. When coal fire is used to heat the plastic greenhouse to reduce the source of toxic gas, the fuel should be fully burned as much as possible, and a chimney should be installed on the stove to export the harmful gas to the outside of the shed.

4, the use of non-toxic plastic film does not use the plastic film mixed with more plasticizers as a shed film.