Evaluation of a crop water stress index for irrigation scheduling of bermudagrass

This study was conducted to assess crop water stress index (CWSI) of bermudagrass used widely on the recreational sites of the Mediterranean Region and to study the possibilities of utilization of infrared thermometry to schedule irrigation of bermudagrass. Four different irrigation treatments were examined: 100% (I1), 75% (I2), 50% (I3), and 25% (I4) of the evaporation measured in a Class A pan. In addition, a non-irrigated treatment was set up to determine CWSI values. The status of soil water content and pressure was monitored using a neutron probe and tensiometers. Meanwhile the canopy temperature of bermudagrass was measured with the infrared thermometry. The empirical method was used to compute the CWSI values. In this study, the visual quality of bermudagrass was monitored seasonally using a color scale. The best visual quality was obtained from I1 and I2 treatments. Average seasonal CWSI values were determined as 0.086, 0.102, 0.165, and 0.394 for I1, I2, I3, and I4 irrigation treatments, respectively, and 0.899 for non-irrigated plot. An empirical non-linear equation, Qave=1+⌊6[1+(4.853 CWSIave)2.27]−0.559⌋Qave=1+6[1+(4.853 CWSIave)2.27]−0.559, was deduced by fitting to measured data to find a relation between quality and average seasonal CWSI values. It was concluded that the CWSI could be used as a criterion for irrigation timing of bermudagrass. An acceptable color quality could be sustained seasonally if the CWSI value can be kept about 0.10.