Alkaline by-products generated in the pulp and paper industry can be used to reduce soil acidity. However, the low Mg and intermediate Na values in these residues can negatively affect the bioavailability of some nutrients and soil properties. Before recommending them, it is therefore imperative that their effects on the soil be evaluated. The objective of this study was to quantify the soil chemical composition and vertical mobility of cations due to application of alkaline industrial residue in different forms, in comparison to dolomitic limestone. The experiment was carried out in a laboratory, with a Haplumbrept, from 2005 to 2006, using leaching columns (30 x 10 cm diameter). The treatments consisted of a 4 x 2 x 2 factorial design, including two previous values of soil pH with one control each, two alkaline compounds (industrial residue or dolomitic limestone) and two application methods (surface applied or soil incorporated). Ten percolations were performed, at weekly intervals, in a volume of 300 mL of distilled water per week, corresponding to a total amount of 380 mm rain. 60 % of the Na added leached from the soil-incorporate by-product, but this leaching decreased to 12 % when it was applied on the soil surface. The addition of alkaline residue did not cause leaching of Ca, Mg or K, and dolomitic limestone leached only 2.4 % of the Ca and 7.2 % of added Mg, demonstrating the low vertical mobility of these cations when applied from basic compounds to variable charge soils. The previous elevation of the soil pH decreased cation leaching substantially due to the increase of the soil negative charges. Given the rainfall conditions in southern Brazil, the amount of Na added will disappear from the plow layer in less than one year after its application, so this product should not negatively affect any chemical or physical soil property.
leaching; sodium; alkaline by-product; limestone
