LED Plant Lighting Status

- Jun 17, 2019-

Plant lighting is one of the most widely used fields in LED agriculture. In greenhouse, plant tissue culture, plant factory and mushroom production, LED can be used to replace traditional light sources in many occasions. At present, the main applications of LED plant lighting sources include:
(1) Greenhouse light supplement:
Light is one of the most important environmental factors for crop growth. Dutch scholars believe that "1% of the light is 1% of the yield", and the importance of visible light in crop production. The illumination of greenhouse itself is much lower than that of open field. Especially in winter and spring season and weather conditions such as continuous shade, rain, snow and fog, the situation of insufficient illumination will be more obvious, which will often restrict the yield and quality of greenhouse crops. Artificial supplement light has become an important means of efficient production of greenhouse. At present, the artificial supplementary light sources in greenhouse mainly include high-pressure sodium lamp, low-pressure sodium lamp, metal halide lamp and fluorescent lamp. The infrared and green spectral components of these light sources are relatively large, and the red and blue spectral components required for crop photosynthesis are relatively small, the utilization rate of light energy is low, the energy consumption is high, and the operation cost is high. In recent years, with the rapid development of LED light source, especially the successful development of high-power LED chip products, it provides a new means for greenhouse lighting. There are two kinds of common LED greenhouse supplementary light sources, one is vertical illumination LED point light source, the lamp is similar to high-pressure sodium lamp round head lamp structure; the other is the side illumination LED band light source interpolated between plants. At present, the use of LED light source for artificial supplementary light in greenhouse is still in a small-scale stage.

(2) Plant Factory:
Plant factories are regarded as one of the important technological means to achieve revolutionary breakthroughs in agriculture in the 21st century by controlling the temperature, humidity, illumination, CO2 concentration and nutrition of plant growth process in facilities with high precision through computers and realizing the high-efficiency agricultural system of continuous crop production annually. At present, there are two main types of plant factories: one is solar and artificial light plant factories with greenhouse as the main body, whose light source system is completely consistent with the greenhouse supplementary light; the other is artificial light plant factories with closed thermal insulation space as the main body, which is the way of plant production in a fully artificial environment and is less affected by the external climate. With continuous annual production, high space utilization rate and output per unit area, high power consumption and high operating cost of air conditioning and lighting are also important bottlenecks restricting its development. Consequently, energy saving and consumption reduction have become an important issue in artificial light controlled plant plants.

The application of high efficiency LED light source is an important means to solve the energy consumption problem in plant factories. At present, the main artificial lighting sources in plant factories are high pressure sodium lamp and fluorescent lamp, which have high energy consumption, large heat dissipation and high operating cost of air conditioning. The emergence of LED provides an important means to solve the energy consumption problem of plant factories. Since 1994, Japan has tried to use LED as lighting source for plant factories. The combination of red LED with 5% blue LED with wavelength of 660 nm has been successfully used for lettuce and rice cultivation in artificial plant factories. In 1997, Watanabe Bozhi used water-cooled template LED light source to grow vegetables in plant factories. The cultivation method was nutrient liquid film method (NFT). Lettuce and celery were selected for crops. Vegetables could be harvested after two weeks of planting. On the cultivation area of 800 M2 (8m x 10m x 10 layers), 5900 vegetables were produced every day and 1.5 million vegetables were produced annually. In February 2009, Japan Fairy Angel announced that it had begun to develop a vegetable factory "Angel Farm Fukui" with LED lighting manufacturer CCS. In September 2009, the Institute of Agricultural Environment and Sustainable Development of the Chinese Academy of Agricultural Sciences successfully developed the first intelligent LED plant factory in China, with a building area of 200 m2. The production of artificial light seedling by using LED has achieved good results. (3) Plant group culture seedlings:
Tissue culture of plants is a rapid propagation technology that can obtain large numbers of seedlings of the same quality in a short time through large-scale production. Because of the rapid propagation speed of group culture seedlings, which are not constrained by external climate, region and time, it has become an important means of genetic breeding, germplasm resources protection and virus-free rapid propagation. However, the traditional light source for tissue culture is fluorescent lamp, which has low light efficiency and high calorific value, and its energy consumption cost accounts for 40%-50% of its operation cost. The application of new energy-saving light sources, high light efficiency and energy consumption reduction has been a major advantage in the field of plant tissue culture. In recent years, all countries in the world are actively using LED as tissue culture light source. Two kinds of banana tissue culture light sources (45,60,75 micromol.m-2.s-1) with 80% red LED+20% blue light and 90% red LED+10% blue light were developed. The experiment showed that 80% red LED+20% blue light LED (60 mu).