Common air damage of flowers in greenhouse and its prevention and control

In winter and spring, the air temperature is on the low side, the air permeability of the greenhouse is poor, and the air is not released in time, and the internal and external gas can not be exchanged in time, so that the flowers in the greenhouse will be harmed by harmful gases, the light ones will be yellowed, dry tip, poor growth, reduced ornamental value, and the heavy plants will die. In this paper, the common gas damage types and prevention methods of flowers in greenhouse are briefly described as follows: (1) ammonia and nitrogen oxide gas hazards: these two substances are mostly caused by improper fertilization. Such as the application of ammonium bicarbonate or a large amount of urea, ammonium sulfate and a large amount of immature organic fertilizer, coupled with high temperature, drought and poor ventilation, often cause a large amount of ammonia in the greenhouse in a short time and cause plant poisoning. Performance, from the edge of the leaf to produce water-like spots, like boiling water scalded, and then gradually brown, dry, shedding, such as cut rose will often show the above symptoms. Nitrogen oxide gas damage mostly showed symptoms after 10 days of fertilization, and irregular green and white spots occurred in the damaged leaves, such as African chrysanthemum, Mantianxing and so on. Prevention and control methods: ammonium bicarbonate is not allowed in greenhouse, urea and ammonium sulfate should be applied less when topdressing, and it is best to dilute it into 500 times liquid with water before pouring; organic fertilizer can only be applied after full ripening. (B) carbon monoxide and sulphur dioxide gas damage when coal fire or sawdust combustion is used to heat plastic greenhouses, a large amount of carbon monoxide and sulfur dioxide are produced due to insufficient combustion or blocked flue and high sulphur content in the fuel. The damaged leaves showed obvious dotted, massive or flaky white spots, and the leaf tip and margin were yellow and withered. Such as stars, carnations and so on. (3) the harm of toxic gas in some plastic films, some plasticizers and stabilizers (such as 2-isobutyl phthalate, etc.) are added in the production process, which can emit toxic gases such as ethylene and chlorine and harmful substances such as 2-isobutyl phthalate in the process of use. The data show that when the content of harmful substances such as 2-isobutyl phthalate in water droplets reaches 10 to 20 mg / L, the water droplets are atomized and absorbed through roots or leaves, which will produce serious toxic effects. When the concentration of chlorine in the air reaches 0.1 mg / L, the leaves will appear white or light brown irregular spots, and in serious cases, the leaves will become white or even fall off. When ethylene in the protected land reaches 1 mg / L, it will make the leaf tip and leaf edge of flowers yellow, and even become white and dry. Prevention and control methods: timely ventilation, the use of sunny noon time to open the vent, so that the air is smooth, even in rainy and snowy weather, should also be a short time of ventilation, as far as possible to reduce harmful gases in the shed. (4) excessive use of fumigant (such as chlorothalonil or dichlorvos) or excessive fumigant (dichlorvos), and unreasonable use of fumigant (such as formalin and methyl bromide can only be used in the empty shed, it is easy to cause drug damage in the growing season), it will also lead to yellowing of leaves and dry tips of flowers and plants. Prevention and control methods: correct and rational use of the above-mentioned agents.