Beware of harmful gases that harm greenhouse crops
In recent years, due to the improper operation of fruit farmers and vegetable farmers in the production and management process, some harmful gases have harmed the greenhouse crops, which has reduced the yield and quality of fruits and vegetables, and brought economic losses to fruit farmers and vegetable farmers. Here are the symptoms, main sources and preventive methods of several major harmful gases.
1. Ammonia and nitrogen dioxide
Hazard Symptoms: Causes the leaves to turn yellow and gradually turn brown until the entire leaves die. Main sources: unfertilized organic fertilizers and the application of excess nitrogen fertilizers and waste gas from chemical plants. Prevention method: Keep away from the chemical plant construction shed; apply fully decomposed organic fertilizer, apply fertilizer as little as possible; remove the damaged leaves in time, strengthen fertilizer and water, temperature management, pay attention to ventilation and ventilation; also spray 1% vinegar on the back of the leaf Reduce the symptoms of the hazard.
2, nitrous acid gas
Hazard symptoms: Water-soaked markings appear on the leaf margins and veins of the affected leaves, slowly turning into white spots or plaques. After two or three days, the leaves are dry. Main source: Excessive application of available nitrogen fertilizers, resulting in excessive acidification and salinization of the soil. Prevention method: mainly apply fully decomposed organic fertilizer to avoid excessive application of available nitrogen fertilizer.
3. Ozone gas
Hazard Symptoms: Mottled or greenish spots are formed on the leaf surface of the leaves. The spots vary in size from light brown to dark brown to black, sometimes the leaves are early or the plants are dwarfed. Main source: Oxygen in the greenhouse is produced by ultraviolet radiation from sunlight. Preventive methods; keep away from the chemical plant construction shed; apply fully decomposed organic fertilizer, apply fertilizer as little as possible; remove the damaged leaves in time, strengthen fertilizer and water, temperature management, pay attention to ventilation and ventilation.
4. Carbon monoxide and sulfur dioxide
Hazard symptoms: whitening between the leaf margin and the veins, formation of spotted, and even bleaching of the entire leaf. The main source: the exhaust gas from the large factory, the shed is heated by the fire, and the unfertilized organic fertilizer is applied.
Prevention method: Do not build a shed near the big factory; try not to warm the fire, set the flue of the heating furnace to be tight; apply fully decomposed organic fertilizer; pay attention to ventilation and ventilation; spray 0.5% lime water to alleviate the hazard .
5, ethylene and chlorine
Hazard symptoms: yellow and dead between the leaf margins or veins of the leaves. Main source: shed film. Prevention method: Use a new shed film for ventilation for a few days.
6, hydrogen fluoride
Hazard symptoms: The leaf margin or tip of the leaf is water-soaked and gradually turns yellow-brown or dark-brown. Main source: Exhaust gas from chemical plants. Prevention method: Do not build a shed near a large factory.
7, excess carbon dioxide
Hazard symptoms: thickening of the leaves or causing curling, severe deformation of the leaves, or even wilting, decreased photosynthesis.
The main source: artificially increased carbon dioxide. Prevention method: According to the situation of the shed, the carbon dioxide is reasonably applied.
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