Substâncias húmicas e relação com atributos edáficos

Abstract

ResumoEste trabalho teve como objetivo caracterizar a distribuição das substâncias húmicas (ácidos fúlvicos livres, ácidos húmicos, ácidos fúlvicos e humina) e atributos edáficos em perfis de solos de diferentes regiões do Brasil, que foram objeto de estudos de reuniões de correlação e levantamentos de solos realizados pela Embrapa e outras instituições. As amostras foram selecionadas e fracionadas seguindo conceitos da IHSS. A fração humina apresentou os maiores valores de C em todos os perfis, seguida pelos ácidos fúlvicos livres. Nos perfis em ambientes com altitudes elevadas o clima (Cwa, Cfb, Cwb) favoreceu a formação dos ácidos fúlvicos livres. Quanto às propriedades químicas, em ambos os horizontes foram verificados coeficientes de correlação positiva entre o hidrogênio e o conteúdo de carbono orgânico, r=0,58* e r=0,83**, para os horizontes A e B, respectivamente. Dentre as substâncias húmicas a de melhor correlação com o conteúdo de carbono orgânico foi a fração humina, com r=0,89** e r=0,91** para os horizontes A e B, respectivamente. Foi observada correlação positiva (p<0,05) entre a areia grossa e os C-FAF, C-FAH, C-HUM e a relação C-EA:C-HUM, nos horizontes A, indicando que a textura mais arenosa de alguns horizontes superficiais favorece a formação destas substâncias húmicas. O teor de C nos horizontes superficiais e subsuperficiais e a distribuição das substâncias húmicas variaram com a pedogênese e a altitude.Palavras-chave: Matéria orgânica do solo, granulometria, classificação de solos. Humic substances and relationship to soil attributes AbstractThis study had as objective to characterize the distribution of humic substances (free fulvic acids, humic acids, fulvic acids, and humin) in soil profiles from different regions of Brazil, that had been object of studies of correlation meetings and soils surveys carried through by Embrapa and other institutions. The soil samples were selected and fractionated following concepts recognized by the IHSSS. The humin fraction presented the highest values of C in all the profiles, followed by the free fulvic acid fraction. In the profiles located on high altitude the climate (Cwa, Cfb, Cwb) favored the formation of free fulvic acid. As for the chemical properties, both horizons showed positive correlation coefficients between hydrogen and organic carbon content, with r=0.58* and r=0.83** for A and B horizons, respectively. Amongst the humic substances the humin showed the best correlation with the organic carbon content, with r=0.89** and r=0.91**) for A and B horizons, respectively. A positive correlation was observed between the coarse sand fraction and the C-FAF, C-HAF, C-HUM and the relation C-EA:C-HUM in the A horizons, indicating that the coarse texture of some surface horizons favors the formation of these humic substances. The organic C content in the surface and subsurface horizons and the distribution of humic substances varied with pedogenesis and altitude conditions.

Spatialization of Fractions of Organic Matter in Soil in an Agroforestry System in the Atlantic Forest, Brazil

“…Figure 2C shows higher carbon content in the C-HUM fraction than in the other fractions (Figures 2A and 2B). This result corroborates those from tropical climate studies, in which C-HUM is identified as the fraction with the greater carbon reserve in soils (EBELING et al, 2011), and also indicates the presence of recalcitrant OM. This fraction is directly linked to the mineral part of the soil, while C-FAF and C-HAF are equivalent to OM from the labile forms (FONTANA et al, 2011).…”

Carbon and Nitrogen Stocks and Humic Fractions in Brazilian Organosols

“…The N content ranged from 1.4 to 23.3 g kg -1 (10.8 ± 5.4 g kg -1 , mean ± sd), whereas the Nst in the histic horizons ranged from 0.6 to 6.5 kg m -2 (3.1 ± 1.6 kg m -2 , mean ± sd). These results corroborate the assessment of Ebeling et al (2011) about chemical properties of Organosols from different regions of Brazil, which exhibited an average N content of 10.9 g kg -1 . The highest Nst contents were found in Organosols cultivated with crops, most likely due to N fertilization.…”

“…The dynamics of C and N and their fractions have been intensively studied in mineral soils, but few studies have assessed the agricultural potential of Organosols in tropical climate conditions by characterizing the humic substances and their association with chemical and physical properties (Ebeling et al, 2011). Data on the association between C (total and/or in humic fractions) and physical properties of Organosols are scarce.…”

Spatial distribution of organic carbon and humic substances in irrigated soils under different management systems in a semi-arid zone in Ceará, Brazil

“…In recent decades, many studies have been conducted on humic substances in Brazil (LEITE et al, 2003;LOSS et al, 2006;EBELING et al, 2011;VALLADARES et al, 2011). However, only a few studies have been conducted on humic substances in northeastern Brazil, mainly by Cunha et al (2009) and Souza et al (2012).…”