Recent advances in light emitting diode (LED) technology have resulted in an explosion of systems and features that have caught the eye of the green industry. The main advantages of LED lamps for our industry include:
1) By combining LEDs producing different colors of light, it is now possible to produce almost any desired light spectrum.
2) The light spectrum can, in some cases, be adjusted to tailor to specific plant needs during different growth stages.
3) There is potential for significant electricity savings.
4) Their different heat output (convective heat versus radiant heat) allows for much closer placement of the lamps to the crop canopy (in some cases the LED lamps are placed within the plant canopy).
The latter advantage overcomes the challenges associated with the inverse square law (intensity diminishes by the square of the distance) and results in most of the generated photons to be emitted in the direction of the plant canopy (and not to the floor, sidewalls, or the roof).
The efficacy (defined as the number of photosynthetically active photons emitted per unit of electric energy consumed; μmol/J) of LED lamps designed for horticultural application has steadily increased, and several models now have values that exceed the efficacies of the best HPS lamps. While efficacy numbers are just one parameter a grower should consider when deciding whether a particular lighting system would work for them, they are expected to further increase as new designs are brought to market by various manufacturers. As a result, it seems inevitable that LED lamps will be the dominant lamp type for horticultural applications in the not-too-distant future.
The relatively rapid changes in the lighting landscape, and the often expensive purchase prices for LED lamps, have resulted in a wait-and-see attitude among many growers. Researchers have been scrambling to conduct new research trials and provide answers to the many questions growers have. However, the sheer number of lighting possibilities and the large number of crops that are grown, make this a tedious and long process.
Growers are encouraged to conduct their own trials to compare the impacts of LED systems with the lighting system they currently use. Researchers will continue to use a variety of outreach methods to discuss their latest findings, and combined with the results of their own trials, growers can determine the best approach for their particular situation.
Several researchers have recently developed a new product label that includes key information about lamps designed for horticultural applications. The new label is intended to be included on product packaging so that greenhouse growers have easy access to key information needed to make informed purchasing decisions. (An example of this new label is shown on this page). The label includes information about several key operating metrics (electric power requirements and consumption), light output (photon flux density) across important wavebands, PAR efficacy and heat generation, spectral output (represented as the normalized photon flux density), and the PAR distribution at a specific mounting height. The label also includes information about key ratios used for the study of photobiology. Finally, the label includes metrics that allow for comparisons with lamps designed for human vision applications, despite the fact that these metrics have little specific importance for horticultural lighting applications.
We hope that this label will be adopted by the lighting manufacturers that develop lamps that are used to grow crops and that the label will be a useful tool to growers interested in supplemental lighting for crop production.