Ground-Based Spectral Reflectance Measurements for Efficacy Evaluation of Aerially Applied Glyphosate Treatments

1. Ground-Based Spectral Reflectance Measurements for Efficacy Evaluation of Aerially Applied Glyphosate Treatments Huihui Zhang1, Yubin Lan2, Ronald Lacey1, W. Clint Hoffmann2, Daniel E. Martin2, Brad Fritz2, Juan D. López Jr.2 1.Department of Biological and Agricultural Engineering, TAMU 2.USDA-ARS, College Station, TX

2. Introduction Advanced aircraft and aerial application technology allow aerial application applicators to improve application accuracy and efficiency, which saves time and money for the farmer and the pilot. Aerial and ground-based remote sensing technology

3. Introduction (cont.) • Use glyphosate for weed control in agricultural production systems • Evaluation of glyphosate efficacy of application for weed control with different aerial spray technologies • Aerial imagery • Ground-based sensor and data collection

4. Introduction (cont.) • Spectral reflectance properties of vegetation in visible and near infra-red wavelengths (400 -1300 nm) - detect weeds against a soil background, as the weeds and soil have significantly different spectral reflectance characteristics - detect plant stress, as stress usually results in an increase in visible reflectance and a decrease in NIR reflectance.

5. Introduction (cont.) • Ground-based sensors are typically used for ground truth measurements. • Ground-based sensors may collect real time spectral reflectance data or calculate the Normalized Difference Vegetative Index (NDVI), which is a good indicator of vegetation, crop biomass and health in agricultural applications. NDVI= (NIR – Red) / (NIR + Red)

6. Introduction (cont.) Red and NIR stand for the spectral reflectance measurements acquired in the red and near-infrared regions, respectively. Healthier crop canopies will absorb more red and reflect more near infrared light than stressed or unhealthy canopies, and consequently have higher NDVI values.

7. NDVI Sensor • Greenseeker HandHeld Data Collecting and Mapping Unit (NTech Industries, Inc. ) • Internal illumination • Wavelength 660nm & 770nm • Provide data to determine NDVI and Red/NIR ratio

8. Spectoradiometer • FieldSpec HandHeld (Analytical Spectral Devices, Inc.) • A useful tool for detection and monitoring of crop growing status • Collect spectral data from the target ranging from blue, green, red and NIR wavebands • Reflectance spectra of healthy plant canopy

9. Objective • The objective of this study was to characterize glyphosate efficacy when it was applied with conventional and emerging aerial spray nozzles based on use of ground-based spectral reflectance data.

10. Spectrum Electrostatics

11. CP Nozzles

12. Rotary Atomizers

13. Experimental Design

14. Spray Treatment Setup

15. Spray Mixture • All treatments were made with Helosate PlusTM at 1168 mL/ha and 0.5% V/V R-11 non-ionic surfactant. • Helosate Plus contains 41% glyphosate. • Spray mixture also contained Caracid Brilliant Flavine fluorescent dye at a rate of 37 g/ha.

16. Swath 3 X X X X X Swath 2 Swath 1 300 ft 65 ft Treatment Plot flight tractor • Each treatment plot was three aircraft swaths wide (195 ft) and 600 ft long and was delineated with a disked strip of soil. • Ground sensing system took measurements along the strips which were marked in the center of each treatment plot.

17. Ground Sensing System • The Greenseeker and FieldSpec were mounted on a tractor at a height of 1 m above the ground. • The spectral data collecting in the center swath was used for statistical analysis to avoid the effects of cross contamination between treatments. • Field test were conducted on DAT 1, 8 and 17.

18. Results

19. ANOVA Test Results DAT 1 and DAT 8 • ANOVA test analyzed the effect among treatments. • The results on DAT1 and DAT 8 did not show any significant difference among treatments.

20. DAT 17 • Nozzle type had a significant effect on glyphosate efficacy (p = 0.0315 at α = 0.05).

21. Fisher LSD test • For α = 0.05, Treatment 2, 3, and 4 were significantly different from untreated check (Treatment 5). • Electrostatically charged nozzles powered on, CP-11TT flat fan nozzles and AU-5000 rotary atomizers were more efficacious than the electrostatically charged nozzles powered off in controlling weed populations.

22. Two-Factor ANOVA Test • Two-factor ANOVA was carried out based on data from all time periods. • Both factors- treatment and DAT- are significant at α = 0.1 and α = 0.05 level. • NDVI values in all treated plots were decreased dramatically.

23. Reflectance Spectra DAT1 • A slight reflectance in blue (450-480 nm) and red (600-700 nm) • A little more reflectance in green (500-550 nm) • Much more reflectance in NIR (750-1025 nm) • The reflectance spectra from DAT1 still looks like healthy vegetation

24. The overall changes within the study field were observed from the shapes of the reflectance curves. • Overall decreases in healthy weed area due to herbicidal control resulted in an increase reflectance in the visible wavelength and a decrease reflectance in the NIR. • Treatments 2, 3, and 4 performed similarly.

25. Conclusions • All glyphosate application treatments provided effective weed control as compared to untreated areas at DAT 17. • Electrostatically charged nozzles powered on, CP-11TT flat fan nozzles and AU-5000 rotary atomizers were more efficacious in controlling weed populations.

26. Conclusions (cont.) • Glyphosate herbicidal efficacy under different aerial spray treatments could be differentiated from spectral responses over the visible and NIR spectrum regions. • Overall, the ground-based spectral reflectance data could be used to assess glyphosate efficacy when applied with different aerial spray technologies.

27. -- Thank you --