|Authors: ||R. Moe, S.O. Grimstad, H.R. Gislerod|
|Keywords: ||Supplemental lighting, light requirements, photosynthesis, growth, utilization of light, greenhouse crops|
Supplemental lighting of greenhouse crops has long tradition in Norway.
Research in late 1920ís and early 1930ís indicated that the present available incandescent lamps had unfavourable spectral energy distribution for supplementing the natural light in winter, and that short wave radiation was required to make the greenhouse plant production completely independent natural light.
Extensive experiments with fluorescent lamps and high-pressure mercury vapour lamps concluded that fluorescent lamp generally was more effective than the high-pressure mercury vapour lamps.
The work caused a rapid increase in the use of fluorescent lamp in the Norwegian greenhouse industry from 1950, primarily in plant propagation.
Propagation studies with tomato and lettuce in winter months showed that supplemental light with fluorescent lamps resulted in the most compact and high quality plants and was used to about 1980. High-pressure sodium (HPS) lamps came in the 1970ís and are a more effective than fluorescent and high-pressure metal halide lamps in transformation of electricity to photosynthetic active radiation (PAR) for growth.
The concept of year round production using high photosynthetic photon flux (PPF) providing a high daily light integral (DLI) versus the light intensity concept when considering plant productivity and quality will be discussed.
In order to establish a successful year round production, we have to take into consideration that high rate of photosynthesis, growth and development is based on a very complex interaction between light and several other growth factors (temperature, CO2, air humidity, water supply, fertilization). Recommendation of photosynthetic photon flux (PPF), daily lighting period (DLP) and DLI requirements for propagation and cultivation of some important crops will be given.
Download Adobe Acrobat Reader (free software to read PDF files)
URL www.actahort.org Hosted by KU Leuven