SPAD Chlorophyll Meter in Greenhouse Horticulture. Stephen Stanphill April 12 th , 2013. Introduction. SPAD: (Soil-Plant Analysis Development) Released in 1984 (Minolta Co. Ltd, Japan)
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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 (Cucumissativus L.) • SPAD data was also utilized to predict leaf area in this experiment Y.Y. Cho, et. al. ScientiaHorticulturae, 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
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 GreenSeekerdata 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 Handheld GreenSeeker 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