Carbon and nitrogen mineralization rates were determined in samples from a sandy latosolic Red Yellow Podzolic soil, taken at three depths, 0-20, 20-40 and 40-60 cm, during 10 years of sugarcane cultivation, using plots with and without N fertilization (60 kg ha-1 of N, as urea). N mineralization was measured using the incubation - percolation technique and C mineralization by absorbing the C-CO2 in 1 mol L-1 NaOH. Overall, N mineralization was higher (13%) in the treatment with N fertilization than in that without fertilization during the 20 weeks at the 0-20 cm layer of incubation. There were significant differences among sampling periods over the 10 years of cultivation in all three sampling depths. However, the periods with highest mineralization were not the same for all depths and treatments and did not show any consistent trend. C mineralization was not significantly different between fertilizer treatments. C mineralization curves were more linear than those for N in the last weeks of incubation, suggesting that the mineralization rates stabilized between 8 and 20 weeks. Average mineral C and N produced were 611 and 26, 411 and 17 and 427 and 15 mg kg-1 soil for the depths 0-20, 20-40 and 40-60 cm, respectively. There was no reduction of the N mineralization potential during the period of sugarcane cultivation, even in samples from plots which had not received any N fertilization over that period.
soil depth; N fertilization; incubation; cultivation time