Estimation of Crop Water Stress Index in Almond Orchards using Thermal Aerial Imagery

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An important method for estimating Crop Water Stress Index (CWSI) is by measuring surface temperature of the canopy. A remote sensing method was used to estimate CWSI of an almond orchard in Paramount farm, California. An aerial remote measurement using MASTER (MODIS/ASTER) thermal band data used to measure canopy temperature (Tc). The empirical relationship for canopy- air temperatures difference (Tc-Ta) versus Vapor Pressure Deficit (VPD) represents the crop water stress quantitatively. The results implied that the average value of CWSI for well-irrigated (non-stressed) almonds is 0.24 while the almond yield is affected when the average CSWI values for stressed crop due to lack of irrigation is greater than 0.5. The difference in crop canopy to air temperature (Tc-Ta), measured was negatively related to the VPD [R2=0.96 and p<0.0001]. However, the relationship between (Tc-Ta) and VPD used to develop a non-stressed baseline equation for almonds, which estimates CWSI. Determination of CSWI is useful for irrigation scheduling and water management.

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