Six calcareous soil profiles (P1, P2, P3, P4, P5 and P6) were investigated with regard to their main characteristics of soil organic matter related to structural organization. The effect of degrading processes on these soils was also considered, mainly under intensive cultivation. Based on morphological in situ observation and analytical data, the profiles P1 e P2 showed organic matter with an advanced level of evolution presenting reasonable amounts of low polymerized materials (fulvic acids). Conversely, profiles P3, P4, P5 e P6 showed a high content of well polymerized components. In all soils, humina comprises 50-60% of the humus. Considering the degrading aspects (i.e. cultivation involving intensive soil tillage) observed on the P1 e P2 and the amount and composition of the humic substances, it is suggested that soil organic matter is one of the main factors affecting structural disorganization observed in these soils.
structural desorganization; humic substances; humic acid; fulvic acid; humin; soil degradation