Baselines for Calculating Crop Water Stress Index in Bean Cultivation

Abstract. Efficient irrigation management is vital for conserving water and maximizing productivity, making the crop water stress index (CWSI) a powerful remote sensing tool. CWSI computation requires lower and upper baselines, corresponding to no-stress and severe stress conditions, respectively. This study aims to compare two different methods for determining those baselines. In the empirical method, the non-water-stressed baseline (NWSB) is derived by the linear regression of the canopy-air temperature difference against vapor pressure deficit (VPD) for a well-watered crop. The combined method compares the NWSB coefficients to theoretical expressions to estimate aerodynamic and canopy resistance at potential transpiration. This work used infrared radiometers (IRR) to measure the canopy temperature of bean plants (Phaseolus vulgaris L.) cultivar ‘IAC1850’ under center-pivot irrigation. Since the empirical method is susceptible to fluctuations in meteorological data, an expressive amount of data had to be filtered out. When comparing the two methods, the RMSE is 1.0 °C for the lower baseline and 1.8 °C for the upper baseline. Future studies could use these baselines to provide CWSI maps from thermographic images.