Assessment of soil salinization risks under irrigation with brackish water in semiarid Tunisia

Summary, in English

The salinity problem is becoming increasingly widespread in arid countries. In semiarid Tunisia about 50% of the irrigated land is considered as highly sensitive to salinization. To avoid the risk of salinization, it is important to control the soil salinity and keep it below plant salinity tolerance thresholds. The objective of the present study was to provide farmers and rural development offices with a tool and methodology for predicting, monitoring of soil salinity for a better agronomical strategy. The experiments were carried out in the highly complex and heterogeneous semiarid Kalâat Landalous irrigated district of Tunisia. The field and laboratory measurements of soil and water properties were conducted in 1989 and 2006 at different observation scales (2900 ha, 1400 ha, 5200 m long transect, and soil profiles). Seventeen years of reclamation of a saline and waterlogged soil led to the reduction of average electrical conductivity of the soil saturated paste extract (ECe), measured at 5 soil depths (from 0 to 2 m) below the plant salt tolerance threshold and the dilution of groundwater salinity from 18.3 to 6.6 dS m−1. The variation in soil salt storage (ΔMss = Mss2006 − Mss1989) in the vadose zone was negative, equal to about −145 × 103 ton (≈−50 ton ha−1). During the same period, the salt balance (Siw–Sdw) estimated from the input dissolved salt brought by irrigation water (Siw) and output salts exported by the drainage network (Sdw) was equal to −685 × 106 kg and the Sdw was 945 × 106 kg. Under irrigation and efficient drainage, the soil salinization could be considered as a reversible process. At the transect scale, the high clay content and the exchangeable sodium percentage was negatively correlated to saturated hydraulic conductivity. The textural stratification, observed at soil profile scale, favors accumulation of salt in the soil. Based on the findings related to the multiscale assessment of soil salinity and groundwater properties, soil salinization factors were identified and a soil salinization risk map (SRU) was elaborated. The shallow groundwater constitutes the main risk of soil salinization. This map can be used by both land planners and farmers to make appropriate decisions related to crop production, and soil and water management.

• Author: Fethi Bouksila; Akica Bahri; Ronny Berndtsson; Magnus Persson; J. Rozema; S. van der Zee
• Department/s: MECW: The Middle East in the Contemporary World; Division of Water Resources Engineering; Centre for Advanced Middle Eastern Studies (CMES); LTH Profile Area: Water
• Publishing year: 2013
• Language: English
• Pages: 176-185
• Publication/Series: Environmental and Experimental Botany
• Volume: 92
• Links: http://dx.doi.org/10.1016/j.envexpbot.2012.06.002
• Document type: Journal article
• Publisher: Elsevier
• Topic: Water Engineering; Other Social Sciences
• Keywords: Salt balance; Soil salinity; Long term monitoring; Shallow ground water; Tunisia
• Status: Published
• ISBN/ISSN/Other: ISSN: 0098-8472