Key Technical Points for Light Regulation in Greenhouse Grape Cultivation
In greenhouse grape cultivation, because the light intensity inside the shed is often less than 70% of that outdoors, it has a significant adverse effect on grape growth and fruiting, often causing serious flower and fruit drop, poor fruit coloration, low sugar content, poor flower bud differentiation and other phenomena, greatly reducing grape yield and quality. Therefore, enhancing...
In greenhouse grape cultivation, because the light intensity inside the shed is often less than 70% of that outdoors, it has a significant adverse effect on grape growth and fruiting, often causing serious flower and fruit drop, poor fruit coloration, low sugar content, poor flower bud differentiation and other phenomena, greatly reducing grape yield and quality. Therefore, enhancing the light intensity inside the greenhouse has become one of the key techniques in protected grape cultivation.
I. Greenhouse Design Requirements
1. Orientation. Face south with the back to the north. To make better use of morning light, in regions with severe winter cold and heavy, frequent morning fog, the orientation may deviate 5-10 degrees to the west; in regions where winter mornings are not too cold and fog is scarce, it may deviate 5-10 degrees to the east.
2. Reasonably design the angle of the front roof surface. Actual measurements show that in the northern regions of China, an incidence angle within 40-90 degrees has little effect on light transmittance. Therefore, when actually building a greenhouse, the angle between the greenhouse roof surface and the horizontal can be changed to 23-25 degrees; this not only significantly reduces the roof surface inclination, which is convenient for management, but also greatly reduces the construction cost of the greenhouse. When building a greenhouse in regions north of 40 degrees north latitude, for every 1 degree increase in latitude, the front roof surface angle of the greenhouse must be correspondingly increased by 1-2 degrees. For example, in the Beijing, Tianjin and Tangshan region, the front roof surface angle of the greenhouse should be 21-24 degrees, so that the sunlight transmittance is most suitable for the needs of grape growth. The angle of the auxiliary light-receiving surface should preferably be 60-70 degrees, so that scattered light can be absorbed and the light intensity inside the greenhouse increased.
II. Select plastic film with good light transmittance and keep the film surface clean
Plastic film has a very good ability to transmit ultraviolet light, and blue anti-drip film has the best light transmission performance and is widely used in production. Glass is inferior to plastic film in transmitting ultraviolet light, so it should not be used. When selecting plastic film, the main considerations are its durability, light transmittance, heat preservation and anti-drip properties. If there are water droplets on the surface of the plastic film, the light transmittance decreases by 28%-30%, so anti-drip plastic film should be selected. Multi-layer composite heat-preserving high-light-transmittance greenhouse film EVA remains intact after 18 months of use, has an anti-drip effect lasting 6-8 months, and its heat preservation is also 2°C-3°C higher than ordinary PE film during the day and 1-1.5°C higher at night; after 18 months of use, its light transmittance can still reach 70%. Dust on the film surface must be removed frequently to keep the greenhouse film clean.
III. Lay silver-gray reflective film
Lay reflective film on the north, east and west walls or on the ground of the greenhouse, so that sunlight shining on the film is reflected onto the grape plants, increasing the amount of light received by grape leaves. Laying reflective film on the ground can increase light intensity by 25%, and increase the temperature by 1°C at 1 m below the greenhouse. Laying 200 sq m of reflective film per mu of greenhouse costs 150-200 yuan and can be used continuously for 3 years. This measure is one of the most economical and effective methods for enhancing light, and its effect is especially remarkable for improving the coloration and quality of colored varieties. Before laying the film, the first removal of old leaves should be carried out and the land should be leveled. After laying the film, press it down firmly at multiple points with plastic bags filled with sand and stones to prevent it from being rolled up by the wind or torn.
IV. Install biological sodium lamps to supplement light on cloudy days
Biological sodium lamps can balance the spectral distribution, have high light output, and have a very good light supplementation effect. Experiments have proved that on cloudy days, adjusting biological sodium lamps in the greenhouse to red and yellow spectra is most beneficial to grape growth and the improvement of fruit quality.
V. Whitewash the walls and columns
Whitewashing the back wall, side walls and columns of the greenhouse with lime can enhance the reflection of light, significantly improve the light conditions inside the greenhouse, and to a certain extent play a role in increasing light, raising temperature and improving photosynthetic efficiency.
VI. Spray photosynthetic promoters
After the grape leaves unfold, spraying photosynthetic promoters 4-5 times can significantly promote leaf photosynthesis.