The light intensity in the greenhouse directly affects the photosynthetic efficiency of watermelon, and then affects the sweetness and quality of watermelon. The light intensity in the shed changes due to factors such as weather, regional latitude and time, and increases with the increase of external light intensity.
In the north-south greenhouse, the light intensity in the morning is strong in the east and weak in the west, while in the afternoon it is strong in the west and weak in the east. The difference between the north and the south is small. If a small shed is built in the big shed, the heat preservation effect is improved, but the light transmittance of the multilayer film is reduced by 40% to 50% compared with the single film. The number of columns in the shed, the type of shed film, the old and new, and the degree of pollution can all affect the light intensity in the shed.
To increase the intensity of light in the shed, first try to choose a non-drip film to avoid the influence of dew on the surface of the shed film on the light transmittance. Secondly, pay attention to keeping the shed film clean during management operations, reduce dust, dirt, etc. attached to the shed film to reduce the intensity of light. Third, we must strictly pruning and topping in time to ensure that the light from the top and sides of the greenhouse can enter unobstructedly. Especially for the truss cultivation, the space between the leaves on the top of the shelf and the roof of the shed should be kept at least 30cm. The small shed in the fourth big shed should be removed in time after the temperature in the shed stabilizes to ensure the plant's need for light intensity. Fifth, the silver-gray mulch film on the ground can increase the intensity of the reflected light near the ground, and it should be laid according to the conditions.
When the light intensity in the shed in early spring or rainy weather is too low, additional artificial auxiliary light sources or reflectors can also be considered to ensure the photosynthetic needs of the watermelon.
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