1. SPAD Chlorophyll Meter in Greenhouse Horticulture
Stephen Stanphill
April 12th, 2013

2. 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)

3. 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).

4. 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

5. 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

6. 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

7. Functional Similarities
Non destructive to the plant
Rapid data collection
Can facilitate on-the-spot accurate N determinations

8. 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 Crop Sensor
$495.00

9. Horticultural Application
Cost of handheld Greenseeker unit is much lower than that of the SPAD meter
Faster speed of collection
Ease of use

10. 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

11. Horticultural Application
With larger flower sizes and variations in color, the GreenSeeker unit becomes increasingly ineffective at determining N content

12. 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

13. Solutions Handheld GreenSeeker SPAD Chlorophyll Meter
Segregate test plants for disbudding and NDVI data collection
Forego data collection of mature plants
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

14. 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