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 Crop Sensor $495.00

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 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

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