Assessing soil moisture and salinity dynamics in an irrigated olive orchard using the HYDRUS 2D/3D model

Irrigated agriculture is the world’s largest water consumer, while at the same time water resources are under increasing pressure from rapidly growing demands and climate change. In Greece, about 45% of the total cultivated area is being irrigated and groundwater is the main source of irrigated water supply. Due to the scarcity of fresh water, the islands of Greece face serious problems by saltwater intrusion in coastal aquifers. In these areas, it is a common practice to utilize saline groundwater in irrigated olive orchards. Thus, estimation of all water fluxes temporally and spatially within and out of the crop root zone, and evaluation of issues like salinity are necessary to fully assess the efficiency of irrigation systems and methods. Simulation models can be used to investigate these issues over several seasons and scenarios. In this study, HYDRUS 2D/3D was used to evaluate data measured during one season (2022) in an olive (Olea europaea) orchard in Crete, Greece. The model efficiency was assessed by comparing model simulations against the observations of θ and EC obtained by an IoT-based monitoring system installed in the frame of HORIZON 2020-Agricapture project in irrigated fields of the Merabello area (Eastern Crete). The system includes the monitoring of soil moisture and atmospheric sensors, providing information on irrigation scheduling to farmers. Three IoT-devices were established in the study field, connected with an advanced soil moisture, temperature, and electrical conductivity sensor Teros12 (METER group, Inc. USA) installed at 0.3 m depth. Meteorological data collection was possible through a weather station (Davis Vantage Pro2™) installed in the area. Comparison of simulated against observed θ and EC showed a good precision of HYDRUS 2D/3D model for olive trees irrigation, with the Nash-Sutcliffe and the Root Mean Square Error (RMSE) being within the acceptable ranges. Model results can be used to improve the decision-making IoT system and advise farmers on various aspects of irrigation under saline environment, as, for example, in scheduling irrigation events for leaching salts, to avoid crop damage.

The authors acknowledge contribution of the AgriCapture CO2 - Horizon 2020 project. This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101004282.