Pedogenesis and Variability in Soil Properties in a Floodplain of a Semiarid Environment in Southwestern Sicily (Italy)

Abstract

We performed a pedological study of the variability in soils in a floodplain area of a semiarid region in southwestern Sicily. The objectives of our research were to (i) investigate the role of parent material, erosion, and distribution processes on soil pedogenesis and horizon differentiation; (ii) evaluate the statistical distribution of soil properties; and (iii) interpret these distributions in terms of pedogenic and other processes. Our results showed that not all soil properties examined followed a normal distribution and that even when logtransformed, the degree of normality of the soil salinity data did not improve. Furthermore, principal component analysis was performed to investigate the role of parent material and erosion and distribution processes on soil pedogenesis and horizon differentiation. Although all soils tested had developed on alluvium, great variability was found among them, mostly related to the grain size of the substrates. Soils that had developed on finer alluvium had higher clay content, cation exchange capacity, exchangeable bases, soil salinity, exchangeable sodium percentage, and sometimes organic carbon accumulation with depth because of hydromorphic conditions and chemical stabilization by Ca ++ ions. Soils that had developed on coarser deposits showed a clear differentiation between the topsoil and subsoil in terms of a decrease in clay content from the surface soil to the subsoil. The accumulation of clay on the surface of a floodplain can result in a high risk of loss of productivity because of the significant relationship between clay content, hydromorphic conditions, and exchangeable sodium percentage.