When the temperature is lower than the minimum temperature required for the normal growth of vegetables, the plants will exhibit a series of symptoms, which will affect the growth and development of the plants and cause greater economic losses. Therefore, in the cold, even the cloudy days, the creation of suitable temperature conditions for the growth of vegetables is the basic measures for the management of greenhouses.
First, the symptoms of cold damage
1. Freezing damage. When the temperature in the shed is lower than the low temperature limit of the vegetables can be tolerated for too long, the vegetables will be frozen, and the water in the plants will freeze, causing the cells to die. Only light leaves were frozen, but those with heavy leaves were frozen to death.
2. Cold damage. Also known as cold damage, low temperature barriers. It is because when the temperature in the greenhouse is lower than the optimum temperature for vegetable growth for a long time, the plants appear wilting and grow slowly; the chlorosis of the leaves is yellow-white or the leaves are shriveled; the leaves are dark green, or the leaf margins are dead; it can also cause Falling fruit or forming malformed fruit. Different types of growth and development of the same vegetable, different low temperature range and low temperature duration, different performance of low temperature barriers.
Second, the cause of the cold hazard
1. Due to a sudden drop in outside temperature, it was cold, rainy, snowy, or windy.
2. The design of the shed is unreasonable, the insulation facilities are not perfect or the conditions for sealing are not good.
3. Excessive air volume, excessive air release time; watering at low temperatures; no temporary warming measures; poor thermal insulation or extensive management.
Third, the prevention of cold hazards
1. Coverage method. Can be covered with straw, paper, blankets and other coverings on the plastic film in the greenhouse. A qualified grasshopper can increase the temperature of the greenhouse by about 10°C. In areas with little rain and snow in the winter and spring, blankets can also be used. In rainy weather, the cover can be covered with a plastic film to prevent rain and snow from wetting the cover. In spring, when the temperature changes greatly, it is necessary to pay attention to listening to the weather forecast. In case of cold weather, take timely protective measures and delay the removal of the cover.
2. Hanging the sky. In the shed, several wires are pulled near the plastic film. A plastic film or non-woven fabric is attached to the wire. The distance between the film and the film is 15 cm. The canopy is rolled up during the day and released in the evening, allowing the temperature inside the shed to increase by 3°C to 5°C. The more complete the canopy, the better the insulation effect.
3. Windshield. Hang a thick cotton curtain or straw curtain at the entrance of the shed to prevent the wind from directly entering the shed.
4. Temporary coverage method. In the greenhouse, a small sorghum mulching film can be used to increase the ground temperature by 1°C to 2°C, or a small scaffolding scaffolding of 0.8 to 1 m in height can be built in the shed. After the sun goes down, a small film is placed on the small arch shed. The film was lifted in the morning to increase the temperature in the shed by 2°C to 3°C. The silver gray film works best.
Fourth, the remedial measures after the occurrence of cold damage
1. Freezing damage. When vegetables are severely frozen, they should be replanted in time to avoid delays in farming. When the vegetables are cold, the following measures can be taken:
(1) Avoid light. Frozen vegetables cannot immediately receive light. Grass curtains and other materials are used to cover the films in the greenhouses. Newspapers and other opaque substances can also be used to cover frozen vegetables to thaw frozen vegetables and restore growth.
(2) slowly warming up. Frozen indoor vegetable sheds should not be thawed by adopting rapid temperature increase measures. In addition to shading, appropriate measures such as air release can be taken to increase the greenhouse temperature slowly.
(3) Add water. After the vegetables are frozen, they can be watered in an appropriate amount. It is also possible to spray fresh water on vegetable plants and the ground with a sprayer in the morning immediately after freezing to prevent the ground temperature from dropping and dehydration and drying of the frozen vegetables.
(4) spraying and preventing disease. After the vegetables are frozen, their growth is weak and they are prone to diseases such as gray mold. After the vegetables are restored to growth, the frozen parts are cut off and, as appropriate, sprayed with 50% of Skoda® WP 2000x, or smoked with 10% Sucrolimine.
(5) Strengthen management. After the frozen vegetables resume their growth, they should be prevented from re-freezing, and loosen the soil in time, apply the appropriate amount of fertilizer quickly, and promote plant growth.
2. Cold damage. Carefully analyze and find out the cause of cold damage. According to the types of vegetable crops and different growth and development stages, corresponding countermeasures are taken, mainly controlling the amount of watering, and loosening the soil in time; increasing the lighting time as much as possible every day. At the noon of the cloudy days, we should also unveil the light to improve the shade. The temperature inside the shed.
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