Reasons for the onset of onion seedlings and countermeasures
Onions have always enjoyed the reputation of “Queen of Vegetables†in the vegetable industry, but the onions are not always smooth in the process of planting. Some farmers have reacted to the dried onions. What is going on here? I will tell you why the onion seedlings are dry:
1. Drought
If the water is not watered in time during the onion growth process, especially when the soil is sandy and the organic fertilizer is low, the seedlings are more likely to dry up.
Control points: 1 Add organic fertilizer. 2 According to the water demand of different growth stages of onion, timely and appropriate watering. 3 Onion nutrition must ensure sufficient water and fertilizer.
2, high temperature and freezing damage caused by yellowing
In the summer when the onion is cultivated at a high temperature (above 35°C) or in the rainy days in the morning, there will be a yellow leaf blight. In severe cases, it will cause onion yellow leaf type and white leaf type burnt disease. The leaves turn white.
Control points: 1 In case of high temperature, water should be cooled. 2 Take care to prevent freezing damage.
3, lack of fertilizer and excess cause yellowing and dryness
1 deficiency of fat: when the nitrogen fertilizer is insufficient, the onion leaves are easy to yellow or even die from the bottom up; when the potassium fertilizer is insufficient, the leaves are easily broken from the leaf sheath, and the later stage is yellowing and dry.
2 deficiency syndrome: when the calcium is deficient, the central leaves are yellow, and some of the leaves are dead; in the absence of magnesium, the outer leaves of the onions are yellowed and dried. When the boron is deficient, the young leaves are yellow and the growth is blocked.
3 excess disease: excess boron begins to die from the tip of the leaf. Excessive manganese leaves are slightly yellowed, and the outer leaves are yellow and dry.
Control points: 1 Reasonable supplement according to symptoms. 2 deficiency syndrome can be solved by foliar spray of trace element leaf fertilizer. 3 Do not increase the concentration when spraying micro-fertilizer. And spray evenly.
4, the phytotoxicity caused by yellowing and dryness
Usually, when an insecticide or a bactericide is used, a large area of ​​yellowing is observed due to an increase in the concentration of the drug used to cause onion damage.
Control points: 1 Scientifically grasp the reasonable ratio of drug concentration. 2 Spray evenly when spraying, and the interval should not be less than 3 days. 3 If the phytotoxicity occurs, it can spray 500 times liquid 0.05% green wind 95 or potassium dihydrogen phosphate 500 times liquid, and strengthen management to reduce phytotoxicity.
5, toxic gas hazards cause yellowing and dryness
Under the conditions of greenhouse production, long-term application of solid fertilizers such as ammonium sulfate, ammonium chloride and ammonium nitrate will cause gas damage. When the soil is alkaline, ammonia damage occurs; when the soil is acidic, nitrite gas hazard will occur. In the event of an ammonia hazard, the dry part of the tip becomes brown; when nitrite gas is present, the leaves turn from yellow to white.
Control points: 1 pay attention to ventilation. 2 Add organic fertilizer and use less ammonium fertilizer. 3 When a gas hazard occurs, it can spray 500 times liquid 0.05% of green wind 95, once every 7 days, for 2 to 3 times in a row, which can reduce the harm.
The reasons for the dryness of onion seedlings and the main points of prevention and control are introduced here. I hope that the above contents will help everyone to prevent the dryness of onion seedlings.
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