Humic substances and oxidable fractions of organic matter in different environments in Amazônia Maranhense

Abstract

The realization of soil management, without considering the limitations and potential of space, has contributed to the degradation of these environments, in different degrees, depending on the impact promoted on the soil attributes. This work investigated the levels of carbon (C), chemical, and oxidizable fractions of soil organic matter, in pasture areas with different recovery times, compared to a secondary forest. We evaluated the following forms of management: Secondary Forest (SF), Perennial pasture (PP), Perennial pasture recovered five years ago by the corn consortium + Brachiaria brizantha cv. Marandu (P5) and Perennial pasture recovered eight years ago by intercropping corn + Brachiaria brizantha cv. Marandu (P8). We determined the C contents of the oxidizable fractions (F1, F2, F3, and F4) and the contents and stocks of humic substances of organic matter in the layers of 0.00-0.10, 0.10-0.20, 0.20-0.30, and 0.30-0.40 m. We observed the highest levels of C in humic substances in areas SF, P8, and P5. Regarding the oxidizable fractions, we found in the P8 area the highest levels of C within the F1 and F3 fractions. Through the multivariate analysis employed, it was possible to evidence the following increasing order P8 > SF > P5 > PP of the impact on soil quality. The recovery of the pasture area, eight years ago, provided improvements regarding the accumulation of carbon in the soil in the oxidizable fractions and humic substances.