The aim of this study was to evaluate the variability of chemical attributes of soil, to define the number of single samples required to form a composite sample and to evaluate if the mean fertility values obtained from the composite sample is the same as obtained from the arithmetic mean of single samples. Three series of sampling, each one with 36 samples collected in an Oxisol, were carried out. Samples of the first series were taken 15 m apart from each other, the second one 2.5 m, and the third one 0.42 m. Composite samples were formulated with samples of first series by a homogenous mixture of 4, 8, 14, 20, 28 e 36 single samples, with three replications. The variability of soil chemical attributes did not vary when the area size decreased from 8,100 m² to 225 m². Doses of lime and fertilizer may have the same recommendation, independently if soil fertility was evaluated by chemical analysis of a composite sample or obtained from the arithmetic mean of single sampling. At least eight single samples were necessary to compose a representative sample of the area.
composite sample; single sample; soil analysis
