1. Why does NDVI work?
What biological parameter could I use to make agronomic decisions if it could be estimated indirectly?
Plant Biomass  Nitrogen Uptake

3. NDVI Normalized Difference Vegetative Index
Developed as an irradiance index for remote sensing
Varies from -1 to 1
Soil NDVI = to .25
Plant NDVI = 0.4 to 0.9
Typical plants with soil background NDVI=
NDVI from different sources vary
Bandwidths for Red, NIR vary
Irradiance vs. reflectance based

4. NDVI = (NIR – Red)/(NIR + Red) Red: 660 +/- 15 NIR: 770 +/- 15
Green plants absorb light in the PAR spectral region, which they use as a source of energy. Chlorophyll strongly absorbs visible light (from 0.4 to 0.7 µm) for use in photosynthesis
Plants have evolved to reflect solar radiation in the near-infrared spectral region. Strong absorption at these wavelengths (+700nm) results in overheating the plant and plant tissue damage. Green plants appear dark in the PAR and relatively bright in the near-infrared. Clouds and snow tend to be rather bright in the red (as well as other visible wavelengths) and quite dark in the near-infrared. Cell structure of the leaves, strongly reflects near-infrared light (from 0.7 to 1.1 µm). 

5. Phycoerythrin Chlorophyll b Phycocyanin B-Carotene Chlorophyll a
Short wavelength
High energy
Long wavelength
Low energy
Phycoerythrin
Chlorophyll b
Phycocyanin
B-Carotene
Chlorophyll a
Ultraviolet
Infrared
X-Rays
wavelength, nm

8. Sensor Design http://nue.okstate.edu/History_of_OSU_Sensing.htm
Micro-Processor, A/D Conversion, and Signal Processing
Photo-Detector
Optical Filters
Ultra-Sonic
Sensor
Collimation
Plant and Soil target

9. Chlorophyll Meters
Minolta: SPAD (soil plant analysis development unit ) 501 & 502
light absorbance (light attenuation) at 430 (violet) and 750 nm (red/NIR transition)
no tissue collection
Leaf chlorophyll (SPAD) vs Leaf N concent

10. Phycoerythrin Chlorophyll b Phycocyanin B-Carotene Chlorophyll a
Short wavelength
High energy
Long wavelength
Low energy
Phycoerythrin
Chlorophyll b
Phycocyanin
B-Carotene
Chlorophyll a
Ultraviolet
Infrared
X-Rays
wavelength, nm

11. On-the-go-chemical-analyses
‘SoilDoctor’ selective ion electrode mounted on the shank of an anhydrous ammonia applicator
Electromagnetic induction (EMI)
measurements (Missouri)
predicting grain yield
sand deposition
depth to clay pan

12. Use of EM as a data layer to better predict yield potential

14. Implications
Reports of improved correlation between indirect measures and yield (EMI) versus soil test parameters
Soil testing (process of elimination)
no single parameter is expected to be correlated with yield
K vs yield
P vs yield
N vs yield
pH vs yield

15. White Light Interference Filter Photodiode Phycocyanin Chlorophyll b
B-Carotene
Phycoerythrin
Chlorophyll a
wavelength, nm

16. Normalized Difference Vegetation Index (NDVI)
= NIR ref – red ref / NIR ref + red ref
(up – down)
excellent predictor of plant N uptake
N uptake, kg ha-1

17. Education 27