Applying high resolution visible channels aerial scan of crop canopy to precision irrigation management

Chen, A., M. Meron and Valerie Orlov.

Abstract

Canopy cover (or vegetation cover) serves in irrigation management mainly to determine primary ET (evapotranspiration) coefficient, as radiation interception and evaporative surface area are directly related to canopy cover. Crop size and development with time depends on water supply, therefore crop canopy maps are tools for detection of irrigation systems spatial uniformity. Several aerial scan campaigns were deployed in the Upper Galilee of Israel in the 2017 growing season to follow up and evaluate irrigation uniformity and crop coefficients of peanuts, cotton and olives by RGB scans of a Phantom 4 multirotor unmanned aerial vehicle (UAV).  Foliage intensity and coverage were enhanced by a Green-Red Vegetation Index (GRVI), which is an NDVI like process where the green channel replaced the NIR. Results demonstrated that the GRVI index is suitable for the purpose of determining vegetation cover. Furthermore, the GRVI index yielded better results than the NDVI index, in recognizing phenological crop changes (especially senescence). Therefore, this research proves the applicability of a low cost system of digital camera mounted on a commodity UAV for crop cover and actual, in-field, ET coefficients determination, and irrigation uniformity evaluation.