Perfis de carbono orgânico do solo nas regiões sul e serra do espinhaço meridional, Minas Gerais: modelagem em profundidade

Abstract

Despite the interest in the spatial variability of key soil properties, depth-related variations have only recently received more attention in the literature. Of all soil properties, soil organic carbon (SOC) is perhaps the most depth-related and difficult to understand. Soil data from two regions in the State of Minas Gerais, Brazil, were used to model SOC profiles and identify factors of influence. In both the South and Southern Espinhaço regions, SOC profiles were best described by log functions. Oxisols had higher SOC levels in the surface, which decreased less with depth than in Ultisols, Inceptisols and Entisols. This could be ascribed to the greater depth,permeability and clay+silt content of Oxisols. Based on the regular increase of intercepts and log factors of the equations obtained for increasing clay+silt contents, profile pedotransfer functions were estimated to describe SOC concentrations based on texture and depth of any given soil,confirming the hypothesis that soil texture strongly controls SOC retention in both regions. In addition, SOC profiles could also be described according to Fe2O3 contents (by sulfuric digestion) in soils of the Southern region, suggesting a mineralogical control of SOC retention. Also in the Southern region, the SOC contents of soils located between 1,000-1,200 m a.s.l. were higher than those of soils at lower altitudes. However, the SOC profiles of the Oxisols and nitic Ultisols of both regions were very similar, which may be an effect of higher clay contents in the South region, and of higher altitudes in the Southern Espinhaço mountain region.