What are the supplementary light sources in greenhouses and how to choose them?

The selection of supplementary light source in greenhouse should be based on the following two principles: first, the purpose of supplementary light; The second is the cost performance of the light source. Fill light usually has two purposes. One is to inhibit or promote the flower bud differentiation of greenhouse crops and adjust the flowering period, that is, to meet the needs of crop photoperiod. This kind of fill light generally needs red light, but the illumination is relatively low, so as long as there are dozens of lux of illumination, it can meet the needs, and incandescent lamps are used more. The second is to promote photosynthesis of greenhouse crops, promote crop growth and supplement the shortage of natural light. The requirements of this kind of supplementary light for light source are that the illumination of supplementary light is higher than the light compensation point of plants, generally above 3000lx; The illumination has certain adjustability; Light is rich in red light and blue light; There are some spectral components; Preferably, it is a continuous spectrum similar to sunlight. This kind of fill light mostly adopts high-pressure gas discharge lamp or fluorescent lamp. In addition, different kinds and varieties of crops cultivated in greenhouse have different requirements for light and spectral characteristics. Therefore, when choosing the light source, we should fully consider the types of crops and the demand for light in different growth periods. The following table gives the supplementary parameters of artificial light for several greenhouse vegetables for reference when selecting light sources. In the absence of relevant parameters, it is best to determine the most appropriate supplementary light parameters through experiments.