Watering is one of the most important measures in vegetable management. However, there are specific details such as when to water, whether to water large or small, whether to water during the day or at night, etc. Under the action of temperature and the earth's gravity, the water in the soil is always a dynamic process.
Part of the water poured into the soil will sink, part will be absorbed by plants, and the water on the surface of the soil and the water absorbed by plants will transpire into the air, thereby increasing air humidity. Watering in the morning during the sunny day, after the watering is over, close the air vent, increase the temperature of the shed, will accelerate the evaporation of soil moisture, and then open the vent, the water in the air of the shed is dispersed to the outside of the shed, and the air humidity at night will not be too large. If it is cloudy or watered in the afternoon, the temperature in the shed is low, the evaporation of soil moisture is slow, and the wind and moisture can not be vented, resulting in high air humidity, and at night there are more water droplets condensed on the surface of vegetable leaves, stems or fruits, in the morning, after uncovering the quilt, when you see crystal clear water droplets on the leaves or fruits, you will feel very beautiful, but this beauty will bring trouble to vegetables. Many pathogenic bacteria that inhabit the soil or the air, prefer water, water is the favorite living environment of these bacteria, there are water bacteria to breed faster, easier to pass through wounds or directly invade plant organs, resulting in the occurrence of diseases. For example, the occurrence of cucumber downy mildew, horn spot, gray mold, tomato leaf mold, canker disease, medullary necrosis and other diseases are all serious occurrences in low temperature and cloudy days and high air humidity in the shed.
This requires that water evaporation be avoided as much as possible when watering. There are two specific measures, one is to watch the sky water, and do not water in the afternoon. Watering in the morning on a sunny day, the higher temperature in the shed will make the evaporation rate of soil moisture faster, and with the help of air management, the water can be discharged outside the shed in time, and the air humidity at night will not be very high. However, this is related to the amount of water and temperature level of watering at that time, and measures need to be taken to control it in this regard.
The second measure is to water small and under the film or drip irrigation. Watering large water at one time, more moisture evaporates into the air, especially in the case of low temperature in the shed, it takes a long time for water to transpire slowly, which inevitably leads to more water droplets condensing on vegetable organs at night. Therefore, in production, it is required that when watering greenhouse vegetables in winter, the first is to water small water or drip irrigation, and the second is watered under the film. This not only limits the proportion of water evaporation into the air, but also the water poured under the greenhouse film is difficult to evaporate into the air, and the humidity of the greenhouse air can be better controlled, and the probability of disease will be greatly reduced.