Page 190 - PC2019 Program & Proceedings

PLANT CANADA 2019

S165. Comparison of a supplemental lighting control algorithm and conventional threshold control
for greenhouse tomato production
Poel, B. ; X. Hao ; M. Yelton ; E. Weissman 1
1
2
1
1 LumiGrow Inc.
2 Agriculture and Agri-Food Canada
Recent advances in supplemental lighting technology such as light-emitting diodes (LEDs) and integrated
control systems have the potential for significant yield increases and energy savings in vine crop
production. Beyond the inherent energy savings LEDs have over HPS lighting systems in terms of
efficacy (µmol/joule), LEDs can be implemented into lighting control systems that adjust output based on
ambient light intensity in order to meet a specified daily light integral (DLI). The current standard for
supplemental lighting control is the threshold method, where lighting is on or off based on measured
outdoor radiation and a proving or refractory period, required to preserve HPS bulb life. Because LEDs
can be powered on and off instantaneously as well as dimmed, there is tremendous potential to reduce
over- and under-lighting to meet a target DLI and significantly improve production efficiency.

We compared the performance of a DLI control algorithm that adjusts LED fixture output intensity based
on ambient conditions to meet a preset DLI to a conventional threshold program that turns LED fixtures
on or off based on global radiation recorded by an outdoor pyranometer for winter production of high-
wire tomatoes. Despite the threshold control consuming approximately 90% more energy compared to the
DLI control method, yields were not significantly different suggesting current supplemental lighting
strategies need to be re-examined in terms of set points and delivery methods.

Brian Poel (bpoel@lumigrow.com)

S166. Evaluating the impact of Inter-canopy LED Lighting on the production of Bush Beans within
a Controlled Environment
Stoochnoff, J. ; T. Graham; M. Dixon
*
University of Guelph

The challenge of high-density controlled environment agriculture is to maintain homogenous environment
conditions throughout the plant’s life cycle. As the crop matures, a dense canopy of leaves can challenge
uniform light distribution. The upper leaves attenuate incident light from the primary overhead source and
as a result, the lower leaves receive less light and photosynthesis in these leaves is reduced. Intercanopy
LED lighting can supplement the amount of light available to lower canopy leaves, thereby maintaining
photosynthetic activity and increasing net photosynthetic rate overall. Intercanopy LED lighting has been
shown to increase yield of greenhouse vine crops such as tomato and cucumber. To date, the effect on
LED intercanopy lighting has not been tested on bush bean (Phaseolus spp). This research project
compared the productivity (fruit/shoot/agronomics) of bush bean grown under fluorescent lighting (300
-2 -1
µmol m s ) with or without the presence of additional LED intercanopy lighting in a controlled
environment growth chamber. Preliminary results of this study will be discussed during the presentation.

Jared Stoochnoff (jstoochn@uoguelph.ca)

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