Sustainable management of coastal saline soils in the Saloum river Basin, Senegal

Abstract

Salinization of soils is one of the major environmental problems facing the world. Frequent tidal intrusions and continuous decrease of annual rainfall support the salinization of soils in the coastal area of the Saloum river Basin, West Central of Senegal, West Africa. This study aimed at appreciating the spatial variability of soil salinity along a levee to backswamp toposequence in the Saloum River basin; in order to assess the constraints and potentialities of these saline soils and propose sustainable soil management strategies. One transect (2.2 km) oriented East-West, including 9 soil profiles located on three topographic units: floodplain, low terrace, and middle terrace was selected. Soil chemical properties (electrical conductivity, pH, water soluble cations and anions) were analysed to estimate the salinity level at each soil horizon (n = 45). Soil pH (3.5-8.5), electrical conductivity (0.01-55 dS m^-1) and water-soluble cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (Cl-, SO₄ ^2-) decrease with altitude. The study demonstrates the close correlation between landscape position and soil salinity illustrated by a two-dimensional salt distribution pattern: horizontal and vertical. The horizontal pattern is appreciable at landscape scale and supports different salinity level between the three topographic positions. The vertical pattern occurs within soil profiles and is closely linked to soil texture and groundwater dynamic. The topographic position exerts thus the major influence on soil salinity along the toposequence. Mulching appears ultimately as the most efficient method in reclaiming these coastal saline soils.

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Keywords: soil salinity, soil management, Saloum river basin, Senegal, West Africa