Both water scarcity and salinity are major obstacles for crop production in arid parts of Tunisia and require adoption of strategies aimed at improving water-use efficiency. Field experiments on deficit irrigation (DI) of table olive, orange trees, and grapevines with saline water (2 dS·m⁻¹) were conducted in the arid region of Médenine, Tunisia. Three irrigation treatments were compared with the farmer’s method (FM) over two years (2013–2014): deficit irrigation (DI75) and (DI50), which received 75% and 50% less water than full irrigation (FI), respectively, and full compensation of the crop evapotranspiration (FI). Measurements included seasonal changes in soil water content, soil salinity, yield, fruit quality, and economic return. Results showed that in-season water limitations, roughly between 700–250 mm, caused significant reductions in yield and fruit weight, but improved the total soluble solids of fruits. Under FI, DI75, DI50, and FM, average yields were 26.6, 20.1, 14.7, and 21.2 t·ha⁻¹ for orange, 4.5, 4.0, 3.1, and 3.5 t·ha⁻¹ for table olive, and 3.8, 3.4, 3.1, and 3.5 t·ha⁻¹ for grapevine, respectively. Soil salinity build up increased linearly with decreasing irrigation water. Irrigation water productivity (IWP), although lowest for FM, was relatively high (3.30–4.30 kg·m⁻³ for orange, 0.65–1.20 kg·m⁻³ for table olive, and 0.74–1.30 kg·m⁻³ for grapevine). Economic evaluation showed that the FI strategy generated the greatest net income (1800–6630 USD·ha⁻¹), followed by DI75 (1350–3940 USD·ha⁻¹), FM (844–4340 USD·ha⁻¹), and DI50 (600–2400 USD·ha⁻¹). The results show an important potential for reasonably sustaining farmer’s income under increased water scarcity.

Crops’ water requirement is generally higher than the annual average precipitation in arid environments characterized by scarce freshwater resources. While using saline water for irrigation can help sustain agriculture in water-stressed regions, several challenges arises 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 is considered as a crop sensitive to salinity. This crop (cv. Spunta) was the subject of long-term studies (2002–2020) conducted during the 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 the soil water balance (SWB) method consisted of the total and/or partial replacement of accumulated crop evapotranspiration (ETc), as derived from climatic data and crop coefficients. 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 the SWB strategy under actual farming conditions, supporting the use of this strategy for irrigation. Appropriate scheduling also seems to be a key element in saving water (15%–22%) and in reducing risks of soil salinization. In the dry environment of southern Tunisia, optimum supply seems to correspond to a replacement of 100% to approximately 70%–80% of ETc. Applying such irrigation levels resulted in a lower salinity buildup in the root zone and higher crop water productivity. Natural salt leaching seems to be more effective under a 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, fertilizer supply, and salt leaching will help in resolving productivity and environmental issues.

FAO’s Aquacrop is one of the most suited models to water limited and saline conditions. It can help to assess management practices and allows developing better informed decisions concerning management and environmental factors that affect crop production. In this study, Aquacrop was used to determine the acceptable threshold of initial soil salinity and the suited period for sowing barley. Three initial soil salinity levels (3, 6 and 8 dS m-1) were evaluated under different initial soil water content for full (FI) and deficit irrigated barley and two contrasting seasons. Barley yield was predicted also for 8 consecutive sowing dates including the sowing dates used by famers. The model simulations were evaluated using statistical indicators (Root Mean Square Error (RMSE), Mean Bias Error (MBE), Mean Absolute Error (MAE) and the coefficient of determination (r2) and the three season’s experimental data. Results show that grain yield and final biomass decrease with delay of sowing date and these reductions were accentuated with high initial soil salinity and the variability of rainfall events. The most suitable period for sowing barley ranging between end of November and the beginning of December. Initial conditions affect yield while the yield reduction started to be considerable (30%) only with the relatively higher level of soil salinity (8 dS m-1) and for dry season and deficit treatment. The comparison between measured and simulated yield and biomass under varied sowing dates and initial soil salinity shows good agreement with RMSE ranging between 0.36 and 1.6 t ha-1, MAE ranging between 0.29 and 1.48 t ha-1, r² about 0.77 and 0.81 for yield and final biomass, respectively. Aquacrop could be a useful tool to determine the optimum barley yield for different restricted factors. Key words: Barley, irrigation, Aquacrop, saline water, sowing date, management practices, arid environment.

Irrigation management to improve smallholder’s incomes for saline conditions Fathia El Mokh 1*, Kamel Nagaz 1, Mohamed Moncef Masmoudi2, Netij Ben Mechlia2 ¹Institut des Régions Arides, 4119 Médenine, Tunisia ²INAT, 43 avenue Charles Nicolle,  2083 Tunis, Tunisia [*]
ABSTRACT Abstract : In the Mediterranean arid regions, the water limitation is the constraint major for agriculture development. Under this condition, one of the most common water quality concerns for irrigated agriculture is saline. The use of this saline water is increasing with the increasing of water scarcity. Its use without integrate management (soil, crop and water) poses high risks of land degradation and crop productivity reduces. Therefore, this study was considered in southern Tunisia to investigate farmer irrigation practices over two years. The impact of irrigation strategies with saline water (6 dS/m) on yield, soil salinity, water productivity and farmer net return were evaluated. Five crops were considered: barley, carrot, fava bean, pepper and potato. The irrigation strategies based on soil water balance method (SWB) which are full irrigation strategy (FI: restore 100% of the crop evapotranspiration) and deficit treatment (DI70: 70% of the ETc covered) were compared to farmer practice (FM). For both seasons, FM strategy caused a significant increase in soil salinity that affects considerably the yield produced for most of the crops compared to the full and the deficit (30%) water supply strategies. The water restriction of 30% improves the total water productivity without affecting yield significantly especially for barley and faba bean where the yield reduction was ranging from 2.5 to 9.5%. Results showed that the practice of cash crops (potato, carrot and faba bean) which have a short cycle improves considerably the farmer incomes compared to the barley crop. The pepper provides also high economic return for farmer but it consumes more water and has a long growing cycle. Based on this analysis, the farmer income can be improve considerably with better irrigation and crop management. Key words: Water management, Salinity, Yield, Water productivity, Farmer return. [*] Corresponding author: elmokh.fa@gmail.com

Efficient water management is critical in modern agriculture due to unsustainable depletion of water resources, intensified by climate change. Digital technologies such as IoT offer opportunities to optimize water use through precise, real-time assessment of water requirements. This study presents ACQUAOUNT-Farm, a real-time platform designed to assist farmers in irrigation planning across Mediterranean environments. The tool integrates on-site IoT sensors (soil moisture, water flow, weather) with a physically based model following the FAO-56 dual crop coefficient approach, embedded within a user-friendly interface. The platform requires minimal input data, providing soil moisture monitoring and scheduling capabilities suitable for non-expert users. ACQUAOUNT-Farm updates daily, reconstructing hourly soil moisture and irrigation needs up to one week ahead and generating an irrigation calendar based on crop-specific water stress thresholds. ACQUAOUNT-Farm was tested on four farms in southern Tunisia for citrus and potato crops (2024-2025). Simulated and observed soil moisture showed good agreement for three out of four farms (R² ≈ 0.65, RMSE ≈ 0.022 m³ m⁻³, MAE ≈ 0.016 m³ m⁻³), with errors below sensor accuracy (0.03 m³ m⁻³) up to two days in all farms, confirming the model's forecasting ability. Compared to farmers' practices, ACQUAOUNT-Farm indicated water savings of 63–65% for one citrus field and 80–84% for autumn potato, while spring potato showed 17–33% savings. In one citrus field, the model confirmed the farmer's deficit irrigation strategy. These results suggest that ACQUAOUNT-Farm has the potential to support farmers in Mediterranean regions in reducing water withdrawals.