Fracionamento químico e caracterização de substâncias húmicas extraídas de solos submetidos a plantio direto com e sem terraceamento

Abstract

Since agriculture is one of the main activities in Brazil, it is recognized that some agricultural areas end up not receiving the correct management practices. This work aims to verify whether the type of management implies structural differences in humic substances in soils. Humic substances were extracted from 15 soil samples: 5 from terraced planting areas; 5 without terracing and also 5 soil samples from native forest for control, using the methodology recommended by the International Society for Humic Substances. Humic (AH) and fulvic (FA) acids were characterized by: yield, elemental analysis, FTIR, XRD and TGA. A higher AH and AF yield was observed in soil samples from the native forest. The elemental analysis showed that both fractions, from the three areas studied, had low H/C values, indicating a higher degree of aromaticity or unsaturation. DRX analysis showed that the samples had some mineral constituents. On the other hand, in the FTIR analysis, the presence of several functional groups was observed, in addition to some mineral impurities possibly originating from the soil in natura. For TGA, the remainder of nonvolatilized material at the end of the process was highlighted. However, there were no significant differences in the characterization of humic or fulvic acids from different crop soils.