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Revista Brasileira de Ciência do Solo

On-line version ISSN 1806-9657


GONTIJO, Ivoney et al. Planning the sampling for preconsolidation pressure of a red latosol. Rev. Bras. Ciênc. Solo [online]. 2007, vol.31, n.6, pp.1245-1254. ISSN 1806-9657.

Preconsolidation pressure is currently used as a tool in the study of the soil compaction process. The purpose of this work was to determine the layout and number of samples required for the determination of the preconsolidation pressure (sp) in a Red Latosol, as well as to characterize its variability and spatial distribution using classical statistics and geostatistics parameters. The study was carried out in an experimental farm area, in Lavras, Minas Gerais State, Brazil, conventionally tilled in the last 30 years. The experimental area was 32 x 160 m (5.120 m2) in a regular grid. Samples were collected at 68 equally spaced points (10 x 8 m). Six transects were chosen: four transects with 4 points and two transects with 8 points were sampled to detect short distance variation. Ninety-eight undisturbed samples were collected at a depth of 0-3 cm. The samples were subjected to the uniaxial compression test to establish sp at field conditions. Using classical statistics parameters, the appropriate number of sampling points for sp determination was 10. The highest variability was obtained for sp (CV 14.8 %) and the lowest for water content (CV 12.0 %). In both cases, the soil parameters were normally distributed, and the semivariograms were satisfactorily described by spherical models with a moderate spatial structure, and with spatial ranges of 19.5 and 90.0 m, respectively. Under similar study conditions, intervals equal to the spatial range should be used for sp determination in future studies in order to reduce the sampling effort and increase representativeness. Although the ratio of the spatial dependence of the studied variables was intermediate, the spatial range must be taken into consideration when planning sampling. Field slope influenced the sp values directly. The constructed preconsolidation distribution map identified regions with high and low compaction susceptibility. These results will be useful to decide where machine traffic on the soil should begin as to avoid additional problems in the soil structure.

Keywords : soil compaction; geostatistics; soil sampling.

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