Effects of Saline Irrigation Water Applications on Evapotranspiration Partitioning and Crop Coefficient of Tomato Grown in Mediterranean-Type Greenhouses

Abstract

Accurate information regarding crop evapotranspiration (ETc) and its components is essential for proper water management. Salinity has become increasingly serious in many parts of the world, affecting the use of saline water in irrigation for various biochemical processes, hence the importance of understanding the effects of soil and water salinity on ETc. This study aimed to determine the transpiration (Tr) and soil evaporation (Es) components that constitute ETc in tomatoes irrigated by drip irrigation and to investigate the effects of irrigation water salinity levels on ETc and its components, as well as on the crop coefficient (Kc) used to determine ETc. In addition, the reference evapotranspiration (ETo) values determined by the measurements obtained with the lysimeter system were compared with the ETo values calculated using the Almeria (ETo_Alm), FAO Radiation (ETo_FAO-Rad), and Hargreaves (ETo_Harg) models. During the spring growing period of 2022, tomatoes were cultivated under four different irrigation water salinity levels: S0 = 0.7 (control), S1 = 2.5 (low), S2 = 5.0 (medium), and S3 = 7.5 (high) dS m−1. The Tr values in S0, S1, and S2 treatments were measured by the sap flow method. Radiation-based ETo prediction models had strong relationships with lysimeter-measured ETo values (R2 > 0.977 and RMSE < 0.53 mm). The results indicated that increasing salinity levels led to a decrease in both Tr and ETc while causing an increase in Es. In the S0, S1, and S2 treatments, Es accounted for 16.3, 45.0, and 36.2%, respectively. Actual Kc values also decreased with increasing salinity. The results indicate that different actual Kc values can be used when calculating evapotranspiration in decision-making processes in greenhouse tomato production in Antalya and when irrigation water with different salinity levels is used. Additionally, actual ETc responses of tomatoes to salinity can be used to manage saline water in irrigation scheduling.