Determining Crop Soil Water Deficit with an UAS

Determining Crop Soil Water Deficit with an UASRemote sensing (RS) techniques have been used to identify crops grown during different seasons and to estimate crop bio-physical characteristics and water use. Images from satellites such as Landsat 5, 7, and 8 have been used extensively to map crop evapotranspiration rates (ET) using a suite of algorithms. However, Landsat satellites have a fixed revisit frequency (e.g., 16 days) and pixel spatial resolution of 30 m for the visible (VIS) and mid-infra-red (MIR) bands while the thermal infra-red (TIR) band pixel size is 100-120 m. Furthermore, some RS of ET algorithms require that the TIR band be corrected for atmospheric effects (not trivial). These characteristics limit the application of satellites to generate frequent ET maps (every three or four days) to be used in soil water balance methods to help manage scarce water resources more efficiently. Therefore, there is a need to investigate alternatives to produce higher spatial and temporal resolution maps. With the advent of Unmanned Aerial Systems (UASs) capable of carrying multispectral (i.e., VIS, TIR) cameras it may be possible to monitor ET more effectively. Thus, this study evaluates the use of ET techniques that can be used with an UAS to estimate soil water content.

Authors: José L. Chávez, Associate Professor, Civil & Environmental Engineering Dept., Colorado State University | Huihui Zhang, Agricultural Engineer, Water Management & Systems Unit, USDA-ARS Fort Collins, Colorado

Keywords: remote sensing, landsat satellite, soil science, crop science, UAS

To determine crop soil water deficit with an UAS, spectroscopy measurements were collected using a Spectral Evolution high resolution field portable spectroradiometer. Spectral Evolution is a leading manufacturer of field-portable UV-Vis-NIR remote sensing spectroradiometers and spectrometers for applications including geological remote sensing, ground-truthing, spectral remote sensing, environmental and climate research, crop and soil research, vegetative studies, forestry and canopy studies, radiometric calibration transfer, upwelling and downwelling measurement and more. Our UV-Vis-NIR spectrometers and spectroradiometers provide the best combination of high resolution and high sensitivity resulting in the most precise field portable instruments available on the market.

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