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