Agricultural Water Salinity of Reclaimed Tidelands in Southwestern Coastal Areas of South Korea

Monitoring of the salinity of agricultural soil and water is necessary for sustainable food production in salt-affected reclaimed tidelands (RTLs). Soil salinity has been extensively monitored; however, little attention has been given to water salinity. In this study, agricultural water salinity of five RTLs located in the southwestern coastal area of South Korea was monitored. A total of 215 water samples were collected from estuary lakes and inland streams in Bojeon (BJ), Goheung (GH), Gunnae (GN), Samsan (SS), and Youngsangang (YSG) RTLs in 2018, 2020, and 2022. Water samples were analyzed for electrical conductivity (ECw) and sodium adsorption ratio (SAR) to estimate the suitability of water salinity for agricultural uses based on the FAO guidelines. The ECw (average: 1.6 - 3.6 dS m-1) and SAR (5 - 8) were highly variable being dependent on RTL locations, water type (lake and stream), and sampling year and month. For rice cultivation, ECw of BJ, SS, and YSG RTLs was lower than the threshold ECw (2 dS m-1) for rice growth; whereas ECw of GN (2.1 ± 1.0 dS m-1) and GH (3.6 ± 1.2 dS m-1) RTLs were higher than the threshold ECw. For upland crops cultivation, both ECw and SAR of five RTLs were much higher than the FAO threshold values (ECw < 0.7 dS m-1 and SAR < 3). Therefore, our results suggest that agricultural water salinity of the study RTLs is not suitable for cultivation of upland crop. Therefore, long-term monitoring of water salinity as well as developments of advanced irrigation-drainage are necessary for diversification of agricultural uses of RTLs.Distribution of ECw and SAR of lake and inland stream of five RTLs. On the right side of the panels, FAO guideline for the degree of restriction on the use for irrigation water is depicted.