SPAD Chlorophyll Meter in Greenhouse Horticulture
Stephen StanphillApril 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
Y.Y. Cho, et. al. Scientia Horticulturae, 2007
• 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
Determining SPAD Significance
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
• Non destructive to the plant
• Rapid data collection
• Can facilitate on-the-spot accurate N determinations
Functional Similarities
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 Crop Sensor
$495.00
Cost
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 problematic for NDVI collection Infrared Image Showing NDVI
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
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
Handheld GreenSeeker • Segregate test plants for
disbudding and NDVI data collection
• Forego data collection of mature plants
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