In the winter, even when the sky is cloudy, hanging a light curtain in the greenhouse can increase the effect of light and temperature. Some farmers in production practice say that this works well, and some say that the effect is not ideal. Why? The survey found that the angle and height of the hanging curtains of each vegetable farmer were not the same. So, how can a reflective screen be reasonable?
The angle and height of the hanging curtain must be adjusted according to the season. In winter, when the height of the sun is small, the light curtain must be hung short, and it is advisable to hang it vertically or slightly to the ground.
If the vegetables have just been planted, the reflective screen will mainly play a role in raising the temperature of the ground and promoting the easing of seedlings. The light curtain must be hung lower and suspended vertically. If the plant is larger and taller, the bottom position of the light curtain should be raised near the top of the plant, and the angle should be slightly inclined to the south at the bottom to ensure that the reflected light level at 8:30 to 9:00 am is basically the same as the ground level. Under normal circumstances, the reflective screen and the ground are maintained at 75 degrees to 85 degrees. When the vegetables are in the seedling stage, the plants close to the light curtain should pay attention to replenishment, so as to avoid strong weather and high temperature when the weather is fine.
In the investigation, the author also found that in order to deal with the problem of too little light in even the cloudy sky, some vegetable farmers suspended the light curtain on the inner surface of the wall (including the back wall and the east and west walls) so as to completely cover the wall. "Since the light-filling effect of the reflective screen is obvious, we will use it more." These farmers explained this way.
Is this really true? The real effect is exactly the opposite. The reflective screen also blocked the illumination of the wall with a large amount of light, thereby reducing the heat storage capacity of the wall, and the nighttime temperature in the greenhouse was not guaranteed. Under normal circumstances, it is sufficient to set up a reflective screen with a width of 2 meters and the length of the canopy on the north wall of the greenhouse. The specific setting method is to pull a wire along the east-west direction along the aisle walkway at a height of 2 meters, cut the two 1 meter wide light curtains on demand, and use a transparent tape to bond the curtain to a width of 2 meters. Then, the upper end of the curtain is folded back, covered with wire, and then fixed with a transparent tape to form a naturally drooping curtain.
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