What kind of plant fill light is good?

Plant fill light I think many friends have never heard of it, plant fill light is based on the law of plant growth, using photosynthesis of plants for photosynthesis. The plant fill light is white to some extent to replace the sun. Everyone knows that plants need photosynthesis. When they grow, they will make up the light energy to the maximum extent, and carry out photosynthesis under the action of light. However, in order to improve agricultural efficiency, in many cases, plant fill light is used instead of sunlight to enhance the photosynthesis of plants.

Plant fill light is a kind of lamp that provides the light source needed for plant growth and development according to the natural law of plant growth, according to the principle of photosynthesis of plants using sunlight, and using light instead of sunlight. Everyone knows the role of the fill light. Here, everyone is reminded that the fill light is just a supplement. Not a substitute for the sun. If you can replace the sun, you should call it "the light."

Plants can only grow when photosynthesis is greater than respiration. This critical point is called light compensation point. For example, if the light compensation point of tomato is 51.6 μmol/s/m 2 , then the effective radiation for photosynthesis must be greater than 51.6 μmol/s/m 2 to function.

Lux is the intensity of the human eye. For plants, it is measured by the intensity of the spectrum of photosynthesis that is contained in the lamp. This is called photosynthetic active radiation, PAR or PPF for short, and PPF and LUX cannot. Conversion. PPFD is the unit area strength of PPF

Typically a 20w T8 tube LED can only provide about 24μmol/s/m2 of PPFD at a height of 30cm from the plant, and at least 3 lamps if used to grow tomatoes. However, the tomato will grow upwards. In practical applications, the foreign greenhouse uses 630w LEDs to hang in a 4m high greenhouse and can only get 90μmol/s/m2 PPFD. Using 600w agricultural sodium lamps can reach 120μmol/ s / m2 or so, and the price is about 1 / 5 of the LED, so the greenhouse mainly uses agricultural sodium lamps.

Let's talk about the light saturation point. When PPFD reaches this point, the photosynthesis rate of plants is the fastest, but beyond this point, it will not grow any more, and even have a reaction. The light saturation point of tomato is 1998μmol/s/m2. The maximum power lamp in the current application is 1000w double-ended agricultural sodium lamp, PPF 2100μmol/s. When hanging in a 6m high greenhouse, the PPFD is only 200μmol/s. Around /m2, the summer noon sun PPFD is more than 2000μmol/s/m2, so any artificial light source on the earth can't replace sunlight.

The light of the plant's fill light is far from the intensity of natural sunlight. As a reference, the sunny afternoon sun illumination is above 100,000 lux, the sunny morning and evening sun illumination is 20000-40000 lux, and the cloudy and cloudy weather illumination is 5000. -30000lux, the illumination of the room near the window but no direct sunlight is 2000-8000lux. Generally, the illuminance required for the growth of green plants is between 20,000 and 50,000 lux. In contrast, plant growth lamps provide low illumination that does not meet the light required for normal plant growth.

A plant growth lamp in the form of an LED is generally formed in the form of a lamp cup and a spotlight by combining a specific ratio of a red LED and a blue LED. Although the current LED technology can achieve higher luminous efficiency (≥100lm/w), the luminous efficiency of red LEDs and blue LEDs used in plant growth lamps can only reach about 20lm/w, which is better than general fluorescent lamps (50- 90lm/w) is much lower, and the unit power price is much more expensive than fluorescent lamps. According to calculations, if you want to use the LED plant growth lamp to reach the illuminance that can meet the normal growth of the plant within 40cm square, about 1000w LED is needed, and the cost is more than 10,000 yuan. This is not as good as using a fluorescent or microwave sulfur lamp.

Experiments have also shown that within a few tens of centimeters, fluorescent light sources cause significant temperature rises in plants and cultivation media and lead to drying. The main cause of temperature rise is radiation, so it is not easy to block. At the same time, the temperature of a single fluorescent lamp during stable operation has reached 60-90 ° C. If a large number of fluorescent lamps are densely installed in order to improve illumination, effective heat dissipation measures must be taken specifically for the lamps themselves. Although LEDs have the advantage of low heat generation, high-power LEDs and LED light groups also need to specifically consider heat dissipation.

Conclusion: If it is used to replace sunlight and provide light for plant growth, existing plant growth lamps have not yet reached a practical level.

Supplement: In fact, in addition to the fill light, providing a higher concentration of carbon dioxide (gas fertilizer) is more effective for plant growth. If you are planting a small plant, you can put it in a foam box with a layer of pumice or bluestone underneath and pour some water. Then put the plant (with pot) on it and cover the foam box with a glass plate. This provides plants with a high temperature, high humidity and carbon dioxide-rich environment. Such sultry plants will grow very fat and quickly.