A laboratory experiment was carried out in a randomized block design with three replications, in which columns with aggregate classes 2.0-1.0; 1.0-0,5; 0.5-0.25 and 0.25-0.105 mm of a typic Haplortox were used. The treatments corresponded to a 2³ x 4 factorial, with soil covering vegetation (savannah and maize); biological activity (with and without soil sterilization with methyl bromide); sources of N with 10 mumol L-1 of N for saturation of the columns (Ca(NO3)2 and NH4CI); and aggregate classes (2.0-1.0; 1.0-0.5; 0.5-0.25 and 0.25-0.105 mm). After seven days of incubation of the columns with aggregates at maximum water retention, percolations were made with water, after two days under saturated condition, totaling six samples (0, 2, 4, 6, 8 and 10 days after the first percolation). In the first eluition, aggregates of 0.25-0.105 mm presented smaller NO3- content in columns containing microorganisms activity and saturation with Ca(NO3)2. In sterilized system, aggregates of 0.25-0.105 mm presented larger NO3- content in the solution. For the saturated columns with NH4CI, in the first eluition the NH4+ content was larger in the aggregates of 0.25-0.105 mm for the combinations of soil covering and sterilization, while, with microorganisms activity aggregates of 0.5-0.25 mm and 0.25-0.105 mm presented the highest NH4+ content.
nitrate; ammonium; oxysol
