Soil sampling viewing the determination of chemical and physical attributes in areas with different pedoforms.

Abstract

In a natural landscape, soils present a wide variation of chemical and physical attributes at the vertical and horizontal directions as a result of the interaction among several soil formation factors. This work was developed in Jaboticabal, a county of the state of São Paulo, Brazil, with the objective of evaluating the variability of chemical and physical attributes in a Red Latosol (eutrustox) under sugarcane cultivation as well of determining the minimum number of samples to be taken for the analysis of those characteristics. The samples for chemical and physical attributes analysis were collected from compartment I (linear) and compartment II (linear, concave and convex), in a grid of 50 points in each compartment, at the 0.0-0.2 m depth. With a variation of 0% around the mean, the values of pH, organic matter, CEC, total porosity, microporosity, bulk density, clay, silt, and sand were found to be dependably obtained using a low number of samples (< 5). Determining Al-saturation, %BS, and soil penetration resistance values a number of samples varying between 5 and 30 is necessary, whereas phosphorus, potassium, calcium, magnesium, macroporosity and saturated hydraulic conductivity determinations call for a high number of samples (> 30). Compartment II presented higher variability than compartment I thus requiring for the evaluation of all attributes a higher number of samples. Additional keywords: kriging; sugarcane; oxisol.