Abstract
Water scarcity and salinization of arable land in Tunisia are forcing the largest water user, the irrigation sector, to modernize and increase its efficiency. This study evaluated the impact of deficit irrigation with saline water in a sandy loam soil cultivated with potatoes in northern Tunisia. The evaluation considered soil salinization and irrigation water productivity in a changing climate by feeding a calibrated model in HYDRUS‐2D/3D with season‐long weather scenarios from one current and two future climate periods. Future weather scenarios were produced by statistically downscaling results from a regional climate model run with two greenhouse gas emission scenarios (RCP2.6 and RCP8.5). Results showed an increase in salt accumulation over the growing season and a potential decrease in crop yield for RCP8.5. RCP2.6 did not, however, result in any significant changes in salt accumulation or crop yield. Even with saline irrigation water, the use of drip technology resulted in a general leaching of salts from the root zone. This was slightly less apparent during deficit irrigation. However, irrigation water productivity was still higher during deficit irrigation than during full irrigation. Deficit irrigation could thus be profitable but long‐term effects should be addressed before making final recommendations. © 2018 John Wiley & Sons, Ltd.