Fathia Elmokh ^1* Kamel Nagaz ¹ Mohamed M. Masmoudi ²

• ¹ Institut des Régions Arides, Medenine, Tunisia
• ² Institut National Agronomique de Tunisie, Tunis, Tunisia

Crops water requirement is generally higher than the annual average precipitation in arid environment characterized by scarce freshwater resources. While using saline water for irrigation can help sustain agriculture in water-stressed regions, it arises several challenges concerning productivity and soil salinization. However, adoption of efficient irrigation techniques such as drip irrigation, irrigation scheduling and deficit irrigation can help optimize water productivity and mitigate salinity problems in irrigated agriculture. In southern Tunisia, potato is considered among the main cultivated horticultural crops due to its high economic value while it's considered as sensitive crop to salinity. This crop (cv. Spunta) was subject of long-term studies (2002-2020) conducted during fall period in the arid region of Médenine. The crop response to full and deficit irrigation with saline water was assessed for several seasons under contrasting climatic conditions. Scheduling using soil water balance method (SWB) consisted in the total and/or partial replacement of accumulated crop evapotranspiration (ETc), as derived from climatic data and crop coefficient. The impact of decreasing amounts of irrigation waters on crop yield and soil salinity with waters having a salinity ranging between 3 and 7 dS.m -1 was evaluated. Results showed improvements in yield (30 to 37%) obtained with SWB strategy under actual farming conditions supporting the use of this strategy for irrigation. Appropriate scheduling seems also to be a key element in water saving (15-22%) and in reducing risks of soil salinization. Under the dry environment of southern Tunisia, optimum supply seems to correspond to a replacement of 100 to about 70-80% of ETc. Applying such irrigation levels resulted in a lower salinity build up in the root zone and higher crop water productivity. Natural salt leaching seems to be more effective under more humid soil profile. Yield decreases and soil salinity increases almost linearly (r 2 =0.60) with decreasing irrigation water amounts. Future work should focus on the integration of management practices when using saline water. Investigating the relationship and interaction between irrigation amounts, cultivar, fertilizers supply and salts leaching will help in conciliating productivity and environmental issues.