This study presents the use of geostatistical analyses for the design of sampling schemes, focusing specially on the anisotropy impacts on the dimensioning of sample units and image generation techniques. The attribute studied was the superficial clay content, measured during November 1998 in a Typic Hapludox, in Campos Novos Paulista (SP). Spatial variability and anisotropy of clay content were determined by examining the semivariograms, which were fit to theoretical models to obtain its parameters (variogram model type, nugget, sill and range). The observed anisotropy factor expressed an oval, or anisotropic, configuration of the influence area related to the sampling points, according to the structure detected for the spatial variability. The anisotropy could be explained by soil intrinsic factors, conditioned by the topography in the formation processes, and extrinsic factors, such as mechanization, partitioning terraces and other managing practices, which are applied in plough lines, transverse to topographic gradient. These dimensions caused the variation of the area of samples representativeness (ha/samples) between the sampling designs, modifying the required density for a given variance level. The ratio of these areas showed the impact of anisotropy on the number of samples required for each desirable level of variance.
GIS-Geographical Information Systems; digital image; interpolation of tabular data; clay content; Typic Hapludox