Prevention and Control Techniques of Freezing Damage to Vegetables and Vegetables in Sheds

The melon vegetable greenhouses in northern China are often attacked by cold spells in the winter and spring. In particular, during the period from mid-December to mid-February of next year, cold currents occur frequently and the extent of cooling is high. If management fails to keep up, it will cause cold damage to the vegetables in the greenhouse. According to observations: the greenhouse temperature of peppers and cucumbers dropped to 12°C, tomatoes dropped to 10°C, and eggplants dropped to 5°C for a long time, causing freezing damage. In light-frozen plants, growth stagnates and plants yellow, and even if they grow back and grow over the winter, they are short, small, and short-noded, often appearing "flower topping" phenomenon. The yield is low and the quality is reduced. Those who are severely affected by freezing will not be able to recover and die if they fail to save. Summing up the experience of various places in recent years, if the following remedial measures are taken for crops that have been subjected to frost damage, a better harvest can still be obtained.
First, a reasonable fertilizer. Applying the fast-acting fertilizer to the frozen plants can not only improve the nutritional status of the crops, but also increase the concentration of the cell tissue fluid, enhance the cold-resistance and antifreeze ability of the plants, and promote the recovery of growth. The use of foliar spray is more efficient than soil topdressing, and should be based on the characteristics of different crops to be sprayed. For melons and solanaceous vegetables, the three elements of nitrogen, phosphorus and potassium are relatively balanced in life. It is advisable to use three-element compound fertilizer, sprayed treasure, and photosynthetic fertilizer. For leafy vegetables, the requirement for nitrogenous fertilizer is the most in life, and a 1%-2% urea solution should be sprayed. If a suitable amount of gibberellin is added, the effect is better. Rhizome vegetables require more potassium, phosphorus, and other elements and can be sprayed with 0.3% potassium dioxophosphate or 1% potassium sulfate aqueous solution. The foliar fertilizer should be sprayed evenly and thoroughly, so that the leaf surface is stained with fertilizer solution. 7 days to 10 days after spraying, spray again.
Second, timely watering. After the occurrence of frost damage, it should be watered in time. Watering can increase the heat capacity of the soil, inhibit the temperature drop, stabilize the air temperature in the surface and the shed, and effectively reduce and control the development of frost damage. The temperature of the well water is higher than that of the ground water. Groundwater should be used for watering, and water should not be used on the ground. The amount of water to reach the plough layer is appropriate, avoid flood irrigation.
Third, scientific ventilation. After freezing damage occurs in the shed, the sheds cannot be heated immediately. If the temperature rises too fast, the frozen tissue will dehydrate and die. After the sun comes out, the ventilation openings should be opened appropriately. After a while, the ventilation openings should be gradually reduced and closed. Let the greenhouse temperature rise slowly, so that the frozen tissue can fully absorb water, promote cell rejuvenation, and reduce tissue death.
Fourth, proper shade. After the plants are frozen, if the plants are directly exposed to sunlight, tissue water loss is likely to occur, and the plants shrink and wilt. In severe cases, the plants will die. Therefore, a layer of light-leaked grasshoppers should be placed on the sheds, and shaders can also be installed in the sheds to reduce the intensity of sunlight exposure. After the evening, cover the outer cover tightly. The next day, the cover will be shaded only during the light period before and after noon, and then it will be transferred to normal management.

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