Determining cwsi to estimate eggplant evapotranspiration and yield under greenhouse and outdoor conditions

ABSTRACT The crop water stress index (CWSI) is the most common index to monitor and assess crop water stress, based on canopy temperature. To calculate CWSI, upper and lower baselines adaptable to different environments are needed. In this study, empirical and theoretical limiting baseline equations were developed to determine eggplant CWSI values at different levels of water deficit and salinity stress.  The limiting baseline and CWSI values of eggplant were obtained under different watering intervals (daily, weekly and every two weeks) and different irrigation water salinity levels (i.e. 0.8, 2.5, 5 and 7 dsm1) for greenhouse and outdoor conditions. The impact of various levels of water deficit and salinity on total evapotranspiration, yield and CWSI was also studied. With the increase of water salinity, a decrease in the slope of lower baseline was met (from 0.195 to 0.146 in the greenhouse and from 0.134 to 0.098 in the outdoor conditions) along with a rise in the upper baseline. Increase in the levels of water deficit led to greater fluctuations in CWSI variations during the growing season. According to the Duncan’s test results, CWSI values were significantly affected by water deficit and salinity in both environments