Soil organic matter and its different pools have key importance in nutrient availability, soil aggregation, and in the greenhouse gas fluxes between the earth surface and the atmosphere. The objectives of this study were: a) to evaluate the effect of maize production systems under organic and mineral fertilization on total organic carbon (TOC) and total nitrogen (TN) stocks and on organic carbon pools (C) in an Acrisol; and b) to estimate the contribution of these systems in the atmospheric CO2 sequestration or emission. The production systems included two levels of organic compost: level 0 (control) and level 1 (40 m³ ha-1); and three levels of mineral fertilizer (0, 1 and 2), which correspond to 0,250 (AM1), and 500 kg ha-1 (AM2) of the 4-14-8 formula. Organic and mineral fertilizer were combined and applied during 16 years. As a reference of the steady state, soil samples were collected from an adjacent area of the same soil type, under secondary Atlantic Forest (AF). Where organic compost was added, the production systems presented higher organic C and N soil storage, light fraction carbon (C LF) and labile carbon (C L) than production systems without fertilization or with mineral fertilizer only. This confirms the importance of organic fertilizer utilization as a management strategy to improve soil quality. However, the soil under AF showed higher values of organic C and N storage and carbon pools than soils under production systems. Due to their higher sensitivity, the stocks of the C LF and C L were more severely decreased than the TOC stocks and thus, may be used as indicators of the anthropogenic impact or the influence of management alterations on the soil organic matter.
soil organic matter; soil management; soil quality; carbon inputs
