Salt affected soils in Croatian coastal agricultural land under changing climate

The Neretva River Delta is one of the most vulnerable coastal areas to soil salinization as a result of climate change, especially sea level rise and seawater intrusion. In 2020, as part of the DELTASAL project (funded by the European Union - European Regional Development Fund), on location Vidrice frequency-domain soil sensors (FDR) were installed at four depths from 25 cm to 1 m monitoring soil temperature, water content, and soil electrical conductivity (ECb) at high temporal resolution. The objective of this work was to assess the seasonal variation of soil ECb considering irrigation and rainfall in mandarin orchards in 2021. During the irrigation season, the mean value of water EC used for irrigation was 2.1 dS m-1 with a maximum value of 2.6 dS m-1 (August). Prior to the irrigation season (January- June), ECb values were stable at all horizons because most salts leached before January 2021 (475 mm of precipitation fell from October 2020 to January 2021). More significant changes in ECb occurred during and especially after the irrigation season. Mean values of ECb before the start of irrigation were 2.4 dS m-1 (25 cm), 3.5 dS m-1 (50 cm), 4.0 dS m-1 (75 cm), and 4.9 dS m-1 (100 cm). After irrigation started, only the mean value of the first horizon was higher than before irrigation (3.2 dS m-1). The most important observation was that the maximum values of ECb changed from 3.2 dS m-1 to 4.9 dS m-1 in the first horizon and from 4.0 dS m-1 to 5.2 dS m-1 in the second horizon. Although the results presented cover only one season, they demonstrate the importance of monitoring soil salinity in irrigated coastal areas, especially for sensitive crops such as citrus, where elevated salt concentrations can lead not only to yield losses but also to more serious consequences such as permanent soil degradation.