The high levels of organic matter in Histosols grant them peculiar characteristics that are contrasting when compared to mineral soils. Due to the strong interaction between organic matter and adsorbed elements, the routine methods in soil fertility may not evaluate properly Histosols soil acidity. The objectives of this study were to characterize and establish relationships between attributes of the sorption complex and soil acidity, in soils with high organic carbon. The study was developed with twelve soil profiles from different Brazilian states, sampled from 2000 to 2002; eleven profiles were classified as Histosols and one as Inceptisol. The profiles were grouped according to formation environment in soils from coastal and river plains, and soils from high altitude mountainous areas and flat highlands. Besides characterization of soil profiles, according to Embrapa methods, pH was measured by different methods. The amount of carbon was measured using an elemental analyzer (C_CHN), and organic matter (OM) was quantified using a furnace. The results showed that pH measured in water, KCl, and SMP solutions might be equally used to evaluate soil acidity. A high correlation between soil pH by SMP and potential acidity was observed. Levels of C_CHN and OM showed significant correlation with pH in water, though negative, and with CEC and H values, these with positive values. The differences in soil acidity between the two soil groups, according to the formation environment, indicate that this separation is important for managing soil acidity, and evaluating Histosols soil fertility.
Histosols; peat soils; soil pH; organic carbon; soil analysis
