The Apodi Plateau is characterized as an important agricultural centre for the state of Ceará, Brazil. Despite the homogeneity of climate, topography and parent material, soils in the area exhibit a great variability in attributes, often on small spatial scales, indicating the need for separate managements systems. The aimed of the present work was to investigate the influence of microrelief on the spatial variability of different particle-size fractions of the soils in the Apodi Plateau. A plano-altimetric survey was conducted in an area of 102 ha, followed by boreholes for collecting soil samples and determining the effective depth. The samples were subjected to particle-size analysis and the data processed with descriptive statistics and geostatistics, using semivariograms and kriging charts. Based on the microrelief, the study area was divided into 3 different surfaces (concave, convex and flat). From the results a clear influence of the microrelief on the distribution of the particle-size fractions was identified. Higher clay-content and greater soil depth were found on the concave surface. These results indicate greater soil-genesis activity in the soils of this area in response to the existing convergent water flows. The occurrence of higher levels of sand and shallower soils on the convex and more elevated surface indicates less soil-genesis activity and a greater intensity of the selective-erosion process. The use of geostatistics contributed to the identification of areas with different soil-management needs, serving as an important tool for decision making, especially when related to irrigation.
Apodi Plateau; Spatial Variability; Microtopography; Soil-analysis
