Crop water stress mapping for site-specific irrigation by thermal imagery and artificial reference surfaces |
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| Authors: | M Meron J Tsipris Valerie Orlov V Alchanatis Yafit Cohen |
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| Institution: | (1) Crop Ecology Laboratory, MIGAL Galilee Technology Center, PO Box 831, Kiryat Shmona, Israel;(2) Institute of Agricultural and Environmental Engineering, Agricultural Research Organization, Volcani Center, Bet Dagan, Israel |
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| Abstract: | Variable-rate irrigation by machines or solid set systems has become technically feasible, however mapping crop water status
is necessary to match irrigation quantities to site-specific crop water demands. Remote thermal sensing can provide such maps
in sufficient detail and in a timely way. In a set of aerial and ground scans at the Hula Valley, Israel, digital crop water
stress maps were generated using geo-referenced high-resolution thermal imagery and artificial reference surfaces. Canopy-related
pixels were separated from those of the soil by upper and lower thresholds related to air temperature, and canopy temperatures
were calculated from the coldest 33% of the pixel histogram. Artificial surfaces that had been wetted provided reference temperatures
for the crop water stress index (CWSI) normalized to ambient conditions. Leaf water potentials of cotton were related linearly
to CWSI values with R
2 = 0.816. Maps of crop stress level generated from aerial scans of cotton, process tomatoes and peanut fields corresponded
well with both ground-based observations by the farm operators and irrigation history. Numeric quantification of stress levels
was provided to support decisions to divide fields into sections for spatially variable irrigation scheduling. |
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