Recently, severe weather such as rain, snow, low temperature and smog have occurred in northern China. Many shacks have improper methods of uncovering grass scorpions, and the size of ventilated sheds has dried leaves and even dead seedlings. Here, remind the majority of farmers and friends, to uncover the grass, should pay attention to science:
First, the morning is unveiled
I have asked many vegetable farmers: What is the basis for unearthing in the morning? The answer is very consistent: the sun shines on the shed and reveals it. To what extent is it revealed? Most shed farmers can't answer. In fact, it is necessary to use the temperature in the shed to judge whether the time for uncovering the grass is appropriate. The method is: hanging the thermometer in the greenhouse, the temperature in the grass shed will be lowered, but the reduction cannot exceed one degree, and more than one degree indicates that the grass is exposed early. However, the temperature in the grass shed was not lowered, indicating that the grass was unveiled late.
Second, afternoon grass cover
At present, the situation of the majority of vegetable farmers in the afternoon is more varied. Some are covered by the sun when they fall, and some are covered by the afternoon from 3:30 to 4:00. In fact, this is not scientific. The time should be determined according to the temperature in the shed. . The method is: when the temperature in the shed reaches 17 ° C ~ 18 ° C, the grass cover will begin to cover, and the temperature inside the shed may rise after the cover is closed, and the temperature rise may not exceed one degree. Emphasis is placed on the temperature of 17 ° C ~ 18 ° C. The grass is related to the transportation of organic matter. Plants produce organic matter through photosynthesis, which are produced during the day and transported to various organs of plants (roots, stems, leaves and fruits) at night. When the greenhouse is covered with grass, the stomata of the crop is closed, and then the transportation begins. The transport speed is directly related to the temperature of the shed. At 17 °C~12 °C, the transportation is completed in 7-8 hours, and if the shed temperature is lower than At 15 °C, it takes 15 to 16 hours to finish, and the organic matter that has not been shipped out of the grass can only be transported until the next night. The warehouse is not vacated, which directly affects the manufacture of photosynthetic products on the second day. great influence.
Third, the long-term yin and clear the grass
Long time low temperature rain and snow suddenly cloudy after cloudy days, do not uncover all the grasshoppers, in case of "flashing seedlings" (a few days of rain and snow did not reveal grass, the crops in the shed did not see light, the leaves are thin and tender, sunny light The transpiration is large, causing the leaves to lose water and wilting, resulting in thin, yellow and tender leaves, and weak fibrous tissue, which is easy to produce phytotoxicity. The area opened up gradually increased, and all of them were uncovered two days later (the shacks of the rolling shutter machine can be opened first, and then gradually increased).
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