In winter and spring, vegetables are cultivated in facilities. When the outside temperature is lower than the suitable temperature limit for the normal growth of vegetables, it will cause frost damage or cold injury. Now the performance and preventive measures of cold hazards are described below.

The main performance (1) leaf damage. It belongs to mild freezing injury. In the cotyledon stage, the damage of the cotyledon appears as chlorosis on the edge of the cotyledon, with “white bordering”, and the true leaf growth is not affected after the temperature returns to normal. After the planting, the short-term low-temperature or cold-air invasion occurs, and the leaf edges of the plants are frozen. Dark green, gradually dry. (2) Root damage. The root growth was stopped and no new roots occurred. Some old roots were yellow and gradually died. A sudden increase in temperature causes plants to wilt or slow down. Plants with severe damage are difficult to recover. (3) Growth point damage. Belong to the more serious freezing injury, often cause the top buds to be frozen, do not send new leaves, if the weather can not be restored after the warm weather. (4) Damage to flowers and fruits. The cold weather during the flowering period of vegetables will affect the pollination and fertilization effects, resulting in a large number of flowering, falling, or malformed fruits.

Preventive measures (1) seedling low temperature hardening seedlings. From the germination of the seeds, the temperature is slightly lower at the time of germination, then gradually increased to the appropriate temperature, and then the temperature is reduced after the seedlings germinate. Seedlings strictly control the temperature, increase the temperature difference between day and night, prevent the seedlings from being slim and weak, and improve their resilience. Seedlings and seedbeds need to be ventilated and exercised at low temperature 2 days before planting. (2) Strictly grasp the time of colonization. In order to promote the timely planting of vegetables after planting, winter and spring should be selected cold head warm weather. (3) Strengthen the heat preservation. After planting, cover the mulch in the shed, buckle a small shed, and conditionally cover the rake. During the cold season, attention should be paid to blocking all gaps and minimizing heat dissipation in the gap. (4) Temporary artificial heating. If the greenhouse temperature is lower than 15°C during the day and less than 8°C during the night, cold damage or freezing injury may occur, and temporary warming measures should be taken at night. The specific method is to ignite fumes such as dry stalks or sawdust in the sheds away from the vegetables, or to burn the honeycomb coal stove, pay attention to timely ventilation, eliminate harmful gases, and heat the lights in the shed, and use the sets of temporary heating Equipment supplements heat energy.

After the management of the low-temperature vegetables suffers from freezing or cold injury, the leaves may be sprayed with water first, and then slowly warming up slowly. At the same time, uncover the mulch, loosen the soil in time, and appropriately control the amount of water to increase the temperature.

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