February 2019 - 30

CONTROLLED ENVIRONMENT
Light maps help growers manage plant growth
US daily light integral maps
By Denise Attaway
Clemson University
Horticulturists across the United
States can use new light management
tools to ensure greenhouse plants
receive the correct amount of light
needed for proper growth.
The U.S. daily light integral maps
(DLI) developed by Jim Faust, a
Clemson University horticulture
associate professor, and Joanne
Logan, a University of Tennessee
biosystems engineering and soil
science associate professor, allow
growers to better manage light their
plants receive.
" For example, a grower can
estimate the number of days per
year supplemental lighting may be
necessary to achieve the desired plant
growth during winter months or how
much shade cloth may be required to
reduce the light intensity delivered
to crops during the summer months, "
said Faust, who is leading the project.
Often, natural sunlight is enough
to help plants grow, but sometimes
supplemental lighting is required,
especially in areas where cloud cover
during winter months does not
provide plants with enough light for
photosynthesis. The new maps might
be able to help growers lower costs by
allowing them to reduce the amount
of supplemental lighting and shade
cloth required to grow healthy plants.
The scientists created a map
for each month for each state,
including Alaska and Hawaii. Data
for the maps were collected using a
satellite radiation model developed
by the National Renewable Energy
Laboratory. This model uses data
to estimate how much light an area
Daily light integral maps can be used to ensure greenhouse plants receive the correct amount of light needed for growth.
Image: Clemson University
receives each hour. These maps
provide high-resolution data for
about every 38 square miles and can
be used to determine the amount of
supplemental lighting plants require.
This is not the first time DLI maps
have been used. The original maps
were published by Faust and Logan in
2002. When the first maps came out,
the DLI concept was not widely used
by professional horticulturists. But,
with affordable sensors, Cooperative
Extension Service outreach efforts,
educational materials and programs,
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professional horticulturists have
accepted the daily light integral
concept and are now commonly
using it, Faust said.
" Today, growers frequently
reference daily light integral
measurements when talking about
environmental conditions and plant
responses to those environments, "
Faust said. " This knowledge has
contributed to improved management
of the light environment in the
commercial production of a wide
range of horticultural crops. "
Greenhouses are major
contributors to the United States
economy. A study by the University
of Florida Institute of Food and
Agricultural Sciences shows nursery
and greenhouse production generate
about $200 billion annually. Called
the " green industry, " products grown
in greenhouses include flowers,
bedding plants, tropical foliage, as
well as vegetables.
To learn more, visit the DLI maps
interactive map at www.endowment.org/
dlimaps. VGN

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February 2019

Table of Contents for the Digital Edition of February 2019