Influence of ground water on soil salinity in the San Vitale Pinewood (Ravenna - Italy)

The aim of the research was to verify the influence of the depth and quality of ground water on soil salinity within the different micro-topographical contexts of the San Vitale Pinewood, in the Ravenna Province (Italy). To this purpose four Entisols, representative of the different local geomorphological positions, were studied. Meteorological data was recorded and soils and ground water were monitored for one year, as to salinity-related aspects and electrical conductivity (EC). The water table depth and salinity have undergone remarkable oscillations with respect to seasonal weather conditions. The electrical conductivity of the ground water (ECw) differently affected the electrical conductivity of the saturation extract (ECe), depending on the distance of the horizons from the water table. In the spring and autumn, when most of the precipitation occurred, both the water table depth and ECw decreased and this provoked an homogeneity in soils horizon ECe values. In summer, due to high temperature and minimum precipitation, a general lowering of the water table was detected to which an increase of surface horizons ECe corresponded. The intensity of such surface soluble salt accumulation depends on the water table depth and is independent from ground water ECw. Both soils located in inter-dune depressions, with a surface water table, but characterized by a different ground water ECw value, presented in summer a significant increase of surface horizons ECe, even if at different values (PZ1 and PZ3). The summer ECe increase in top horizons didn’t occur when the water table lay at more than 1 m beneath the surface, even if strongly saline (PZ4). When the water table was present at an intermediate depth, a slight ECe increase was observed in surface horizons (PZ7). In the PZ4 profile, using a statistical analysis, a relationship was established between the soil ECe and some environmental parameters.