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Why light is more important for ultradwarf than
for bent: what greenkeepers need to know
Micah Woods
Chief Scientist
Asian Turfgrass Center
www.asianturfgrass.com
21 October 2015
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PAR, PPFD, and DLI
What do these mean?
▶ PAR is photsynthetically active radiation. It is the light with
wavelengths from 400 to 700 nm.
▶ PAR is measured instantaneously as a flux of photons within
those wavelengths on a surface of 1 m2.
▶ Instantaneous PAR is the photosynthetic photon flux density,
(PPFD). In full sun at midday in summer, the PPFD will be
about 2,000 micromoles of photons per square meter per
second.
▶ Adding together all the PAR from each second of the day gives
the daily light integral, DLI. For ultradwarf bermudagrass, the
maximum possible DLI is best. For minimum acceptable
quality, the DLI should be at least 30 moles per square meter
per day.
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PPFD meter
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A sunny day, July 14 2015
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Jul 14 00:00 Jul 14 06:00 Jul 14 12:00 Jul 14 18:00 Jul 15 00:00
Average PPFD by hour, µmol m-2 s-1
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A cloudy day, July 1 2015
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Jul 01 00:00 Jul 01 06:00 Jul 01 12:00 Jul 01 18:00 Jul 02 00:00
Average PPFD by hour, µmol m-2 s-1
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2015-07-01 2015-07-02 2015-07-03 2015-07-04 2015-07-05 2015-07-06
2015-07-07 2015-07-08 2015-07-09 2015-07-10 2015-07-11 2015-07-12
2015-07-13 2015-07-14 2015-07-15 2015-07-16 2015-07-17 2015-07-18
2015-07-19 2015-07-20 2015-07-21 2015-07-22 2015-07-23 2015-07-24
2015-07-25 2015-07-26 2015-07-27 2015-07-28 2015-07-29 2015-07-30
2015-07-31
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Average PPFD by hour, µmol m-2 s-1
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Monday, October 19 2015
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Average PPFD by hour, µmol m-2 s-1
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Tuesday, October 20 2015
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Average PPFD by hour, µmol m-2 s-1
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Tokyo: maximum possible (light blue)
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Tokyo 2014: maximum possible (light blue)
and actual (blue)
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light blue: maximum possible
green: maximum with light saturation at 1000
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Tokyo 2014
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light blue: maximum possible
green: maximum with light saturation at 1000
light green: actual with light saturation at 1000
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Tokyo 2014
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light blue: maximum possible
green: maximum with light saturation at 1000
light green: actual with light saturation at 1000
blue: actual with no light saturation
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Tokyo 2014
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light blue: maximum possible
green: maximum with light saturation at 1000
light green: actual with light saturation at 1000
blue: actual with no light saturation
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Jan 2015 Apr 2015 Jul 2015 Oct 2015 Jan 2016
Daily light integral (DLI), mol m-2 d-1
Tokyo 2015
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-120 -100 -80
Longitude
Latitude
Atlanta, GA Augusta, GA Watkinsville, GA
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Mean daily temperature, ℃
2014, Watkinsville (green) and Tokyo (blue)
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Mean daily temperature, ℃
2015, Watkinsville (green) and Tokyo (blue)
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Watkinsville 2014: max possible (light blue),
actual (green)
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Daily light integral (DLI), mol m-2 d-1
Watkinsville 2014: max possible (light blue),
actual (green), Tokyo actual (blue)
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Jan 2015 Apr 2015 Jul 2015 Oct 2015 Jan 2016
Daily light integral (DLI), mol m-2 d-1
Watkinsville 2015: max possible (light blue),
actual (green)
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Jan 2015 Apr 2015 Jul 2015 Oct 2015 Jan 2016
Daily light integral (DLI), mol m-2 d-1
Watkinsville 2015: max possible (light blue),
actual (green), Tokyo actual (blue)
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Fraction of possible DLI
Tokyo 2014
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Fraction of possible DLI
2014, Watkinsville (green)
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Jan 2014 Apr 2014 Jul 2014 Oct 2014 Jan 2015
Fraction of possible DLI
2014, Watkinsville (green) and Tokyo (blue)
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0.00
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Jan 2015 Apr 2015 Jul 2015 Oct 2015 Jan 2016
Fraction of possible DLI
2015, Watkinsville (green) and Tokyo (blue)
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Summary points
▶ ultradwarf bermudagrass can use all the available light
▶ creeping bentgrass reaches its light saturation point at a PPFD
of about 1000
▶ summer temperatures are similar in Japan and the
Southeastern USA
▶ the summer DLI tends to be higher in the USA than in Japan
▶ successful management of ultradwarf bermudagrass in Japan
considers both temperature and light effects on the turf