The objective of this study was to evaluate alterations in the soil chemical attributes and in humic and fulvic acids at a clay extraction site with spontaneous grass vegetation [Brachiaria mutica (Forsk.) Stapf] and aforested with Acacia mangium Willd. Soil samples were collected at 0-10, 20-20 and 20-30 cm depths. A 33 % and 80 % increase in carbon stocks was observed under A. mangium as compared to the B. mutica cover at the 0-10 cm and 20-30 cm soil […]

The organic matter dynamics in Atlantic forest ecosystems must be understood to ensure the efficiency of conservation programs. Chemical characteristics of humic substances are important because they reflect the soil genesis processes and soil management, and can be used as indicator of the organic matter quality. The purpose of this study was to test the organic matter quality as a marker of the soil environment in areas of native Atlantic forest developed on a distrophyc Gleysol and a distrophyc Cambisol […]

According to the system conditions, humic acids act as oxidants or as reductants. In natural systems the electron flow is directly associated with humus content and quality. Electrode potential and oxidation capacity inform about the intensity and capacity of the redox systems. In previous studies it has been assumed that free radicals participate in humic acid redox reactions. In our study six humic acids isolated from composed organic residues were titrated with an oxidant (I2) in inert atmosphere and specified […]

Vermicomposts present a high content of humic substances and their effects on soil properties are well-documented. However, direct effects of humic substances on plant metabolism are less known. The aim of this work was to evaluate the use of humates isolated from cattle manure vermicompost with 0.1 mol L-1 KOH on root growth and ATP metabolism of lettuce seedlings. After germination, lettuce seedlings were treated with different humate concentrations (0 to 100 mg L-1 of C) for 15 days. The root growth and the H+-ATPase […]

Cattle manure availability is one of the most limiting factors for vermicompost production. The effects of the partial substitution of manure with sugarcane bagasse or residues of Gliricidia sepium on the quality of vermicomposts and the bioactivity of their humates were evaluated by analyzing the root growth and H+-ATPase activity of lettuce seedling roots. The substitutions of manure by sugar cane bagasse and legume cover crops residues did not affect the chemical properties of humates. Humates isolated from the different […]

Crop management systems that favor soil organic matter can improve the available nutrient content for plants and reduce the use of industrial fertilizer. Despite the importance of organic compounds as a P source, little is known about its dynamics in tropical environments. The objective of this study was to identify organic P species present in humic acids by NMR 31P analysis in a fine clay Fluventic Eutrochrepts in Campos dos Goytacazes, in the north of Rio de Janeiro State, Brazil, under […]

The sorption of herbicides to soil is a process determinant of its dynamics in the environment. For weakly polar compounds such as acetochlor, organic matter represents the main sorbent in soil. The goal of this study was to evaluate the sorption of acetochlor on soil samples, humic acids and humin from an “Argissolo Vermelho distrófico” (PVd-Paleudult) under no-till and conventional tillage systems. Sorption isotherms were carried out at room temperature and the herbicide concentration was determined by high performance liquid […]

According to their hydrophobicity degree, organic substances can increase the aggregate stability, reducing the rate of water infiltration into the aggregates. Our study investigated the aggregate genesis and stabilization in a Red-Yellow Latosol under organic compound addition with distinct hydrophobic and hydrophilic characteristics. Air-dried samples from the A and B horizons were incubated with different doses of three organic compounds: estearic acid, amid and humic acid purified in accordance to the International Humic Substances Society. The experiment was organized with […]

In the Lakes Region of Rio de Janeiro State, the occurrence of a drier climate creates a peculiar environment where there is a trend of salinization and presence of xeric vegetation. Physical, chemical, mineralogical and micromorphological properties were studied in selected soil transects. The soils are eutrophic as result of nutrient cycling, low weathering degree, and presence of primary minerals with nutrient reserves in their composition. The occurrence of well developed eutrophic soils (Oxisols) under caatinga (xeromorphic vegetation) on the […]

This study aimed to evaluate physical and chemical alterations in a distrophyc Yellow Argisol (Ultisol) presenting loamy to clayey texture and a smooth relief, under different use at the “Favo de Mel” settlement, Sena Madureira county, Acre State, Brazil. At the beginning of the rainy season (October 1999), soil material was collected in the following land use: native forest (control), recently deforested (slash and burn); a two-year old crop of palm tree (Bactris gassipae); and a four-year old Brachiaria (Brachiaria […]