The present study evaluated the effect of nitrogen levels and splittings on the chemical characteristics of a soil cropped with maize in succession to black oats at the establishment of the no tillage system. The experiment was carried out in a Red-Yellow Latosol (typic Hapludox), with 14% of clay in the 0-0.20 m soil layer. The work consisted of two maize crops (2003/04 and 2004/05) and a black oats one in between, as cover crop. The experimental design was randomized blocks in an incomplete factorial scheme, with four replications. Treatments consisted of nitrogen levels (60, 120 and 180 kg ha -1) and one control without nitrogen, besides the splittings (30 or 60 kg ha -1 at sowing, the balance in cover and 60 kg ha -1 at sowing, remaining top dressed). The following soil variables were evaluated: Ca, Mg, K, organic matter, P, H+Al, Al, sum of bases, CEC, pH and base saturation V(%). Ammonium sulfate fertilization top dressed promoted a pH decrease in all treatments after the second maize crop and the increase in the level of N decreased the contents of soil Ca, Mg and K.
