Radiometric Theory and Vegetative Indices

1. Radiometric Theory and Vegetative Indices

2. Variable Rate Nozzle System Decision Making And Agronomic Strategy Computer and Sensor Assembly Direction of Travel Plant Sensor-BasedNitrogen Management

3. Why Optical Sensing in Precision Farming? • Used to quantitatively describe plant or soil status • Requirement: Calibration of spectral parameters to status • Used to characterize boundaries • Physical • Morphological • Requirement: Accurate spatial calibration (1m actual = 1 pixel) Lat/Lon = f(pixel position)

4. Light Sensing Source System Reflected Light Plant or Soil Surface Issues in conducting remote sensing • Variability in light source • Filtering of light along path • Measuring units/calibration of sensing system • Geometry • Spatial and temporal frequency of measurements

5. Fiber-Optic Spectrometer One Spectral Channel at a time Optical Glass Fiber Optical Grating Analog to Digital Converter CPU Element selection Computer Photo Diode Array

6. Fundamentals of Light • Light = Energy (radiant energy) • Readily converted to heat • Light shining on a surface heats the surface • Heat = energy • Light = Electro-magnetic phenomena • Has the characteristics of electromagnetic waves (eg. radio waves) • Also behaves like particles (e.g.. photons)

7. Photo-Chemistry • Light may be absorbed and participate (drive) a chemical reaction. Example: Photosynthesis in plants • The wavelength must be correct to be absorbed by some participant(s) in the reaction • Some structure must be present to allow the reaction to occur • Chlorophyll • Plant physical and chemical structure

8. Silicon Responsivity

9. Primary and secondary absorbers in plants • Primary • Chlorophyll-a • Chlorophyll-b • Secondary • Carotenoids • Phycobilins • Anthocyanins

10. 0.5 Visible Near Infrared Indicator of Available Chlorophyl Reflectance (%) Measure of living plant cell’s ability to reflect infrared light 0.25 PhotosyntheticPotential 0.00 450 500 550 600 650 700 750 800 850 900 950 1000 1050 Wavelength (nm) Plant Reflectance

11. 1 0.9 Winter Wheat at Feekes 5 in potted soil 0.8 0.7 0.6 Reflectance 0.5 0 Nitrogen 0.4 Measure of living plant cell’s ability to reflect infrared light 100 lb Nitrogen/ac Photosynthetic Potential 0.3 0.2 0.1 0 400 500 600 700 800 Wavelength, nm Spectral Response to Nitrogen

12. Soil and crop reflectance

13. Reflectance Indices Based on ratios of Red and NIR Reflectance Red Reflectance: rred = Rred / Ired NIR Reflectance: rnir = Rred / Ired Vegetative Index: Reflectance is primarily a function of target

14. NDVI • Normalized Difference Vegetative Index • Developed as an irradiance index for remote sensing • Varies from -1 to 1 • Soil NDVI = -0.05 to .05 • Plant NDVI = 0.4 to 0.9 • Typical plants with soil background NDVI=0.3-0.8 • NDVI from different sources vary • Bandwidths for Red, NIR vary • Irradiance vs. reflectance based

15. Normalized Difference Vegetative Index - NDVI • Calculated from the red and near-infrared bands • Equivalent to a plant physical examination • Correlated with: • Plant biomass • Crop yield • Plant nitrogen • Plant chlorophyll • Water stress • Plant diseases • Insect damage

16. Detection of Reflected NIR and RED Direction +Sun NIR and RED Modulated Illumination Target GreenSeekerTM Sensor Light Detection and Filtering

17. Calculate NDVI ? Lookup valve setting ? Apply valve setting ? Send data to UI ? Sensor Function Light signal Valve settings Light Light Valves andNozzles detection generation “Sensor”