Evaluation of Crop Water Stress Index (CWSI) for Eggplant under Varying Irrigation Regimes Using Surface and Subsurface Drip Systems

Abstract

The main objective of this research is to evaluate crop water stress index (CWSI) on eggplant under various irrigation regimes applied with subsurface and surface drip systems in the Eastern Mediterranean Region of Turkey. The field experiments were carried out during the eggplant season of 2013, in the experimental fields of Soil and Water Resources Research Unit in Tarsus. In the study, two irrigation systems (surface drip (DI) and subsurface drip systems (SDI)) in main plots; two irrigation intervals in sub-plots (IF3: 3-day; IF6: 6-day) and four irrigation levels in sub-sub plots (Full irrigation, FI; deficit irrigation, DI-50; deficit irrigation, DI-75; and Partial Root-zone drying PRD-50% of full irrigation treatments) were tested in split-split plot design with four replications. Canopy temperatures were measured throughout the growing season with an infrared thermometer (IRT), and vapor deficit of air (VPD) was used for calculating empirical the CWSI. The effect of irrigation treatments on yield, crop growth and juice quality differed. Irrigation methods, irrigation intervals and irrigation levels resulted in significantly different yields. Surface drip performance was superior to subsurface drip considering yield and quality of eggplants. Full irrigation treatment with 3-day interval under the surface drip (IF3 FI) produced the highest yield (78.7 t ha-1), the lowest yield was obtained in subsurface drip IF6 PRD-50 treatment plots (40.9 t ha-1). The highest water use efficiency (WUE) was found in subsurface drip IF6 DI-50 (21.9 kg m-3) and the lowest in subsurface drip IF6 PRD-50 (12.2 kg m-3). The results revealed that eggplant should be irrigated at CWSI values between 0.18-0.20 for high and good quality yields. CWSI can be used for irrigation scheduling for eggplant.