The dispersion of Oxisol samples can be somewhat difficult due to highly stable microaggregates that are not always completely destroyed by chemical and mechanical dispersion. It is therefore important that chemical and mechanical methods are combined, along with the pretreatment of the sample, for complete and stable soil particle dispersion throughout the analytical procedures. Thus, this study aimed to evaluate the efficiency of mechanical dispersion (slow agitation with an orbital shaker - 30 rpm for 16 h, in the presence of coarse sand, and fast agitation with a cocktail shaker type - 1200 rpm for 20 min) and chemical dispersion with NaOH 1 mol L-1, associated to the pretreatment for elimination of the organic matter, regardless of its content in the soil sample, during the routine textural analysis method. For the analyses, 50 completely random samples from the layers 0-0.20 m and 1,15-1,25 m were collected with a Dutch-type auger in an Oxisol. Each sample represented a replication. Results showed major dispersion of the samples with pretreatment for organic matter oxidation. The process of slow agitation was always more efficient in the dispersion of the soil samples as compared to the fast agitation. The pretreatment for elimination of organic matter and mechanical dispersion with slow agitation for 16 hours and 30 g of coarse sand as abrasive was the most efficient in the dispersion of samples collected in the 0-0,20 m layer as well as at 1,15-1,25 m.
particle-size distribution; pre-treatment; slow agitation; texture
