Transcript SPAD Chlorophyll Meter: Greenhouse Application

SPAD Chlorophyll Meter
in Greenhouse Horticulture
Stephen Stanphill
April 12th, 2013
Introduction
• SPAD: (Soil-Plant Analysis Development)
• Released in 1984 (Minolta Co. Ltd, Japan)
• A lightweight handheld meter for measuring the
chlorophyll content of leaves without causing
damage to plants. (Konica Minolta)
Introduction
The SPAD meter
determines the relative
amount of chlorophyll
present by measuring
the absorbance of the
leaf in two wavelength
regions (650 and 940).
Background
• Increasing SPAD
values indicate higher
concentrations of
Chlorophyll per leaf
unit area.
• Each crop has a
unique SPAD range
University of Missouri and USDA-ARS
Determining SPAD Significance
• SPAD values also show linear correlation to other plant
variables.
• Leaf dry weight plotted against SPAD readings in
hydroponically grown cucumbers (Cucumis sativus L.)
• SPAD data was also utilized to predict leaf area in this
experiment
Y.Y. Cho, et. al. Scientia Horticulturae, 2007
Determining SPAD Significance
• Compare SPAD values to N – rich “strips” in greenhouse
• Use predetermined industry or university standards as a
reference
• Collect samples for foliar analysis after SPAD testing to
develop an algorithm for predicting chlorophyll content or
Nitrogen levels
Functional Similarities
• Non destructive to the plant
• Rapid data collection
• Can facilitate on-the-spot
accurate N determinations
Cost
Unit
Cost
SPAD 502 Plus
Chlorophyll Meter
$2,195.00
SPAD 502DL Plus
Chlorophyll Meter with
Data Logger & RS-232
$2,595.00
Greenseeker® Handheld $495.00
Crop Sensor
Horticultural Application
• Cost of handheld Greenseeker unit is much lower than
that of the SPAD meter
• Faster speed of collection
• Ease of use
Horticultural Application
• Flowering plants begin to
interfere with GreenSeeker
data collection at anthesis
• SPAD readings are not
affected by background
reflectance
• Retail floriculture and other
horticultural uses could be
Infrared Image Showing NDVI
problematic for NDVI
collection
Horticultural Application
With larger flower sizes and variations in color,
the GreenSeeker unit becomes increasingly
ineffective at determining N content
Limitations
• SPAD readings cannot
be taken from very
young seedlings
• GreenSeeker would be
much more effective at
determining N values
for flats of many small
plants
Solutions
Handheld GreenSeeker
• Segregate test plants for
disbudding and NDVI data
collection
• Forego data collection of
mature plants
SPAD Chlorophyll Meter
• Determine cost effectiveness
of spending 4 to 5 times
more on a tool that will not
require the extra labor and
inventory loss incurred by
the alternative
Conclusions
• In many ways the SPAD meter is inferior to the more
efficient hand-held Greenseeker unit for greenhouse
horticulture work
• In many horticultural uses however, there may
always be a need for the more expensive SPAD unit