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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Publications at this Location » Publication #212561
Title: Evaluating the Sensitivity of an Unmanned Thermal Infrared Aerial System to Detect Water Stress in a Cotton Canopy

Author
item Sullivan, Dana
item FULTON, J - AUBURN UNIV
item SHAW, J - AUBURN UNIV
item BLAND, G - NASA GSFC

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/23/2007
Publication Date: 1/16/2008
Citation: Sullivan, D.G., Fulton, J.P., Shaw, J.N., Bland, G. 2008. Evaluating the Sensitivity of an Unmanned Thermal Infrared Aerial System to Detect Water Stress in a Cotton Canopy. Transactions of the ASABE. 50:1963-1969.

Interpretive Summary: Airborne thermal infrared imagery is a promising new method for managing crop response to a range of environmental stressors: water, nutrient deficiency, pests, and disease. Until recently, the expense and timeliness associated with acquiring thermal infrared imagery has limited its usefulness and adoption by producers. The objective of this study was to evaluate a less expensive system, an Unmanned AirVehicle (UAV) equipped with a TIR sensor, for detecting cotton (Gossypium hirsutum L.) response to irrigation and crop residue management. The experimental site was located on a 6.1 ha field in the Tennessee Valley Research and Extension Center located in Belle Mina, AL. Treatments consisted of irrigation (dryland or subsurface drip irrigation) and crop residue cover (no cover or winter wheat (Triticum aestivum L.)). Thermal infrared imagery was acquired on 18 July 2006 at an altitude of 90 m and spatial resolution of 0.5 m. Coincident with image acquisition, ground truth data consisting of soil water content (0-25 cm), plant transpiration and canopy cover were measured within a 1-m radius of each sample location. Significant differences in canopy cover and plant transpiration across irrigation treatments allowed testing of the sensitivity of the UAV system. Thermal infrared imagery provided greater sensitivity to small differences in crop response to irrigation and crop residue management compared to ground truth measurements of plant transpiration. Data are promising and suggest that thermal infrared imagery acquired via a low-altitude unmanned AirVehicle can be used as a tool to manage within season canopy stress

Technical Abstract: Airborne thermal infrared (TIR) imagery is a promising and innovative tool for assessing canopy response to a range of stressors. However, the expense associated with acquiring imagery for agricultural management is often cost-prohibitive. The objective of this study was to evaluate a less expensive system, an Unmanned AirVehicle (UAV) equipped with a TIR sensor, for detecting cotton (Gossypium hirsutum L.) response to irrigation and crop residue management. The experimental site was located on a 6.1 ha field in the Tennessee Valley Research and Extension Center located in Belle Mina, AL, where landscapes are gently rolling and soils are highly weathered Rhodic Paleudults. Treatments consisted of irrigation (dryland or subsurface drip irrigation) and crop residue cover (no cover or winter wheat (Triticum aestivum L.)). TIR (7 – 14 µm) imagery was acquired on 18 July 2006 at an altitude of 90 m and spatial resolution of 0.5 m. Coincident with image acquisition, ground truth data consisting of soil water content (0-25 cm), stomatal conductance and canopy cover were measured within a 1-m radius of each sample location. All sample locations were georeferenced using a real-time kinematic (RTK) GPS survey unit. Analysis of sample locations acquired in multiple flight-lines was used to assess the stability and repeatability of the UAV system during an acquisition. Compared to field measurements of stomatal conductance with CV ranging from 2%-75 %, variability in thermal infrared emittance (CV < 40%) was within the observed tolerance of ground truth measurements of stomatal conductance. Significant differences in canopy cover and stomatal conductance across irrigation treatments allowed testing of the sensitivity of the UAV system. A negative correlation was observed between TIR emittance and stomatal conductance (r = -0.48) and canopy closure (r=-0.44), indicating increasing canopy stress as stomatal conductance and canopy closure decreased. TIR emittance exhibited greater sensitivity to canopy response compared to ground truth measurements, differentiating between irrigation and crop residue cover treatments. TIR imagery acquired via a low-altitude unmanned AirVehicle can be used as a tool to manage within season canopy stress.