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 the treatments according to the modified Plan-Puebla III matrix, using doses varying from -0.55 to 10.45 g kg-1 in the experimental range. After 160 days of incubation, the aggregate stability index, mean weight diameter, and the mean geometric diameter of the aggregates formed were measured. Results indicate that the addition of organic compounds with dominant hydrophilic character does not influence the soil aggregate genesis and stabilization, mainly in doses up to 9.90 g kg-1. The addition of organic molecules with a hydrophobic and hydrophilic structure character, such as humic acids, is able to improve aggregation in soils with a high weathering degree.
amid; estearic acid; humic substances; tropical soils
