Spatial estimation of soil salinity with ordinary kriging (Eastern Tunisia)

Irrigation using brackish water is generally practiced in arid regions, because of their limited conventional water resources. However, this use can lead to disastrous impacts, including soil salinization. Therefore, soil salinity monitoring by setting up valuable monitoring tools is essential. This study examines the spatial variation of soil salinity in the public irrigation zone Zelba 1 of the region of Mahdia (Easten Tunisia) using mapping techniques and ordinary kriging. Results showed that the soil of the irrigation zone is isohumic, presenting a sandy-silt to clay-silt texture. It is permeable with hydraulic conductivity values varying between 8 10-6 and 10-5 m/s. Electrical conductivity measurements revealed that the soil is moderately saline at the surface, with values varying between 0.7 and 1.3 dS/m. This salinity increased slightly with depth. The electrical conductivity varied between 1.3 and 1.8 dS/m for layer (120-150 cm), indicating a moderately saline and saline soil. The increasing gradient of the soil salinity is due to the salts leaching following the irrigation. Mapping of the soil salinity revealed a slight spatial variation of salinity in different soil layers. The southwestern part of the irrigation zone is the most affected by salinity, especially in the deepest layers. Electrical conductivity values varied between 1.6 and 1.8 dS/m. The low salinity observed in the north of the irrigation zone, could be explained by the fact that this part is closer to the water well. It receives more water, explained by the overflow of water from basins accelerating salts leaching to deeper layers.