January 2022 - 30

PRODUCTION
Light It Up. Black It Out.
Improved climate control and plant growth using LED lighting
and screens: a technological match made better together.
BY JOLI A. HOHENSTEIN
T
he three standard methods to control greenhouse climate are
through the management of humidity, temperature and light
- the end goal being a uniform environment optimized for
your specific crop. As a grower, you're focused on carefully managing
greenhouse conditions to ensure crop productivity, maximize yields and
maintain a robust bottom line. But are your production tools working
together synergistically or operating separately?
Supplemental lighting and use of various screening technologies are
powerful tools to manage light, energy balance and climate fluctuation
in the greenhouse. However, there is no one-size-fits-all approach to
implementing one technology or the other, or a combination of the two. So,
customizing applications based on your unique situation is the first crucial
step in using these technologies in tandem. In order to best understand
joint applications of LED supplemental lighting and screening systems, it
helps to take a closer look at each of them separately.
EXPANDING YOUR TOOLKIT: LEDS
LED lighting is quickly becoming the technology of choice for growers
today because LEDs enable growers to 1) customize light spectrum,
2) decrease heat production, 3) reduce energy consumption at the
same light output, and 4) increase light output at the same energy cost.
These benefits allow growers using LEDs to have more control over their
light environment and climate conditions, which can be especially
advantageous when using greenhouse screening systems.
Plants interact with light very differently than the human eye. Plants
most efficiently use light in the range from blue (400 to 500 nm) to deep
red (600 to 700 nm). This is the range of colors or light spectrum that
provides the most PAR, or photosynthetic active radiation - it's the range
they use to grow and produce at maximum potential. HPS has a fixed output
spectrum, so, unlike LEDs, spectral optimization isn't possible.
The most efficient LEDs in the market to date are twice as efficient as HPS
in converting electricity to usable light. At the same energy consumption
as an HPS installation, LEDs can provide up to double the PAR light output.
LEDs, therefore, produce much less heat, which of course is critical when
incorporating screening into the greenhouse, as screening can impact heat
30 JANUARY 2022 GPNMAG.COM
The most efficient LEDs on the market are twice as efficient as HPS in
converting electricity to usable light.
retention. For example, Philips LEDs emit up to 40% less heat per watt
compared to HPS lamps, and up to 67% less radiant heat - the heat that
transfers to plant canopies and other surfaces. Thus, plant temperatures are
lower, and plants are healthier. It's not uncommon for crops to be 2 to 4° F
cooler under LEDs compared to HPS. Overall, due to the lower radiant heat,
growers can use LED lights much longer in the production season and still
reduce energy consumption of the lighting installation.
Studies continue to demonstrate that LEDs provide numerous benefits
to plant quality and growth due to spectral optimization and increased
efficiency. Trials at Ball Horticultural Co. show that using LEDs decreased
liner height on average by 1 cm when compared to HPS-grown plants,
meaning that fewer PGRs are needed. A second trial at Fernlea (Ontario,
Canada) showed increased light levels with LED at the same energy
consumption as HPS. Using LEDs also resulted in decreased time to
transplant, shorter rooting cycle and reduced production time. The
difference in root mass and root intergrowth was visually noticeable in all
varieties. With the increase in available light from LEDs, rooting time was
decreased by two weeks, and plants were ready to sell at week 6-7 instead
of week 8. If you produce 52 weeks per year, this would result in two extra
turns per year.
http://www.GPNMAG.COM
January 2022

Table of Contents for the Digital Edition of January 2022
