Mac OS 10.3.9J Adobe Illustrator 10J
SPAD-502_Eback.ai 2007.7.5
AHIDPK
Printed in Japan
9242-4817-41
2003 KONICA MINOLTA SENSING, INC.
13
The SPAD-502 determines the relative amount of chlorophyll
present by measuring the absorbance of the leaf in two
wavelength regions.
The graph at right shows the spectral absorbance of chlorophyll
extracted from two leaf samples using 80% acetone.
From the diagram, it can be seen that chlorophyll has absorbance
peaks in the blue (400-500nm) and red (600-700nm) regions, with
no transmittance in the near-infrared region.
To take advantage of this characteristic of chlorophyll, the
SPAD-502 measures the absorbances of the leaf in the red and
near-infrared regions. Using these two transmittances, the meter
calculates a numerical SPAD value which is proportional to the
amount of chlorophyll present in the leaf.
Determining when additional fertilizer is necessary
A decrease in the SPAD value indicates a decrease in the
chlorophyll content and nitrogen concentration. This decrease
may be due to a lack of nitrogen available in the soil. This
problem can be solved by adding fertilizer to the soil.
For example, it was determined from past experience that for
Sasanishiki rice plants a SPAD value of 35 or above was
desirable to produce a target yield of 600kg/10a. During the
differentiation and formation of ears, a period of rapid plant
development, the SPAD value fell to between 29 and 32,
indicating that additional fertilizer was necessary.
Type: Handheld meter for measuring chlorophyll using optical density
difference at two wavelengths
Measurement sample: Crop leaves
Measurement system: Optical density difference at two wavelengths
Measurement area: 2
×
3mm
Light source: 2 LEDs (light-emitting diodes)
Receptor: 1 SPD (silicon photodiode)
Display: Measurement data: 3-digit LCD with decimal point
Data number: 2-digit LCD
Data memory: Space for 30 data sets
Controls: Power switch, AVERAGE key, ALL DATA DELETE key,
ONE DATA DELETE key, and DATA RECALL key
Power source: 2 AA-size alkaline-manganese (1.5V) batteries
Battery line: More than 20,000 measurements
Minimum interval between measurements: Less than 2 seconds
Accuracy: Within
±
1.0 SPAD unit (at room conditions, SPAD value
between 0 and 50)
Repeatability: Within
±
0.3 SPAD units (SPAD value between 0 and 50)
Reproducibility: Within
±
0.5 SPAD units (SPAD value between
0 and 50)
Temperature drift: Less than
±
0.4 SPAD units/
°
C
Temperature range: Operation: 0 to 50
°
C; Storage: - 20 to +55
°
C
Dimensions: 164
×
78
×
49mm (6-7/16
×
3-1/16
×
1-15/16 in.)
Weight: 225g (7-15/16 oz.) (not including batteries)
Other: Warning buzzer; User calibration function
Specification subject to change without notice
Checking the nutritional condition of plants
The chlorophyll present in the plant leaves is closely related to
the nutritional condition of the plant. As can be seen from the
graph below, the chlorophyll content (represented by the
measured SPAD value) will increase in proportion to the amount
of nitrogen (an important plant nutrient) present in the leaf. For a
particular plant species, a higher SPAD value indicates a
healthier plant.
Theory
Applications
3.5
3.3
3.1
2.9
2.7
2.5
2.3
2.1
1.9
1.7
24
26
28
30
32
34
36
38
40
42
Leaf-blade nitr
ogen concentration
y =0.079 x - 0.154
r =0.908*** n =68
Measured SPAD value
1984
1985
9.1
9.5
10.3
10.8
12.5 13.0
35
7.1
7.10
7.20
7.30
8.14
30
25
20
15
10
5
0
40
35
30
25
Measur
ed SP
AD value
Young ear
formation period
Young ear
growth line
Fully formed
ears appear
Ear differentlation
period
Ear fertility
(1mm)
(3mm)
(8cm)
(16 -18cm)
Sasanishiki rice plant development
Bursting
period
Days before fully
formed ears appear
Date(month.day)
400
500
Ultra-
violet
Wavelength
Infrared
600
700(
nm
)
Trancemittance
A
B
SPECIFICATIONS
