Standards needed for LED lighting in greenhouses

Many lighting companies market their LED (light-emitting diode) products with claims of delivering an optimal “light recipe” that often consists of a combination of wavelengths and color ratios, such as a 4-to-1 red to blue ratio on the spectrum (colors of a rainbow).

Plant scientists often use this information to evaluate the potential effects of lamps on plant growth and development. But standardised procedures on how to calculate these ratios are lacking, according to a study soon to be published in the journal Acta Horticulturae.

Make indoor crop production more sustainable

“The more efficient supplemental lighting sources are, the less electric power growers need to finish their crops,” said senior author A.J. Both, a professor and extension specialist in controlled environment engineering in the Department of Environmental Sciences in the School of Environmental and Biological Sciences at Rutgers University-New Brunswick. “We hope to help make indoor crop production more sustainable and affordable.”

Increased energy efficiency can have a big impact on the bottom line, and information about new crop lighting strategies will help the burgeoning indoor farming industry, Both said.

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LED lighting in a tomato greenhouse. – Photo: Anne van der Woude

Multiple lighting options

Recent advances in energy-efficient LED technology provide the horticultural industry with multiple lighting options. But growers can’t easily compare technologies and LED options because of a lack of independent data on how lamps perform. That study led to a proposed standardised product label allowing for comparisons of lamps across manufacturers.

Spectroradiometer

The new study recommends using a spectroradiometer, an instrument that measures light output across a specific range of wavelengths. Using such an instrument, various light ratios can be calculated. The researchers reported substantial differences in light ratios comparing sunlight with common lamps, including LED, high-pressure sodium, incandescent and fluorescent lamps used for plant lighting.

The researchers hope that their work will contribute to the development of standard definitions for specific wavebands (ranges of wavelengths) that are important for plant growth and development.