Do water dynamics and land use in riparian areas change the spatial pattern of physical–mechanical properties of a Cambisol?

Abstract

Changes in land use in riverside ecosystems added to the flood and ebb regimes of rivers modify the spatial variability of the physical–mechanical attributes of soil, making it more susceptible to degradation processes, especially during the rainy season. The aim of this study was to evaluate the impact of the use of a Eutric Cambisol, which was cultivated with banana trees, on the pattern of spatial variability of physical–mechanical attributes of the soil under two states of consistency in riparian zones of the Ribeira de Iguape River, São Paulo, Brazil. After the flood period, soil samples were collected from 0.0 to 0.2 m soil depth up to 200 m perpendicular from the river. The study of the spatial variability of soil attributes is considered to be one of the principles of precision agriculture enabling site-specific management. Such data can be used for interpolation, the use of inverse weighted distance (IDW) was chosen, a widely used deterministic method for multivariate interpolation. The following soil attributes were measured: particle-size distribution (clay, silt and sand), water content, bulk density (initial and preconsolidation pressure), cone index, compression index and preconsolidation pressure. The effects of flood and ebb periods on the resilience of these attributes in the Ribeira de Iguape River were evaluated by subjecting the soil to solid and plastic states of soil consistency. The pattern of spatial variation of the physical–mechanical attributes of the Eutric Cambisol was modified: spatial continuity in the soil attributes was greater under smaller water contents (ebb) and less, i.e. greater spatial variation, under flood conditions. The physical and mechanical qualities of the Eutric Cambisol were more affected in the soil closer to the water body. Extreme changes in the load-bearing capacity of the soil with high solid states and weak plastic states consistencies show its susceptibility to structural degradation, mainly under the river flood regimes.