Simulation models are essential instruments to understand soil organic matter dynamics and the turnover of its pools in tropical soils. The objectives of this study were: (a) simulate the effects of maize production systems under organic and mineral fertilization on soil organic matter dynamics of an Ultisol using the Century model; (b) to compare total carbon (TOC) and total nitrogen stocks (TN) and the carbon pools (C) measured in the laboratory and estimated by the Century model for the surface soil layer (0-20 cm). The study area had been part of the Atlantic Forest (FA) until 1930. After that it had been used for maize/bean production up to 1984, when the field experiment was set up. The treatments included a combination of three levels of mineral fertilizer at doses of 0, 250 and 500 kg ha-1 of the 4-14-8 formula and two levels of organic fertilizer (animal manure with soybean and bean straw) at doses of 0 and 40 m³ ha-1. Laboratory determinations included TOC and TN, microbial biomass C representing the active C pool and carbon of the light fraction representing the slow C pool. The passive C pool was determined by difference. The Century model was parameterized with data from the present experiment and from literature, whereas the simulations of the dynamics of TOC, TN and the active, slow, and passive pool included land use changes between 1930 and 2050. The Century model estimated a decrease in TOC, TN and the different carbon pools between the slash and burn of the Atlantic Forest until the establishment of the field experiment. Only in the treatments with organic fertilization it was observed a recovery of these pools. Biomass carbon and the carbon of the light fraction were more sensitive to changes in management than TOC. This highlights the relevance of these pools in studies of organic matter dynamics, particularly in tropical soils. Measured and simulated values of TOC (in Mg ha-1 of C) were well correlated (R² = 0.93; p < 0.01). This was also observed for the active (R² = 0.84; p < 0.05), the slow (R² = 0.87; p < 0.05) and the passive (R² = 0.91; p < 0.05) C pools. Both measured and simulated values of TN (in Mg ha-1 of N) were well correlated (R² = 0.93; p < 0.01). The Century model showed a good performance to simulate soil organic matter dynamics in tropical soils.
Century model; carbon pools; soil organic carbon; tropical soils
