Influence of fulvic acid on the stability of aggregates and melon root in shadow-house/Influencia de los ácidos fulvicos sobre la estabilidad de agregados y la raíz de melón en casa sombra/Influencia dos acidos fulvicos sobre a estabilidade de agregados e a raiz de melao em casa de sombra

Leonardite is an oxidized form of lignite carbon, which is obtained from fossilized organic materials and is used for the extraction of fulvic acids (FA). The addition of FA improves soil structure, but the behavior of the structure after adding FA is scarcely known. The objectives of this study were to determine the influence of fulvic acids derived from leonardite in increasing aggregate stability in a Calcisol under shade house conditions, and to evaluate the morphology of the root xylem during the phenological development of melon plants (Cucumis melo L.). Three treatments were compared: soil without FA solution application (FA0), FA solution at pH6 (FA6) and at pH7 (FA7). Aggregate stability (As) and bulk density (Bd) were evaluated as soil variables, whereas, in plants, development and xylem area were determined. Results showed statistically significant differences in aggregate stability, as well as an increase in the root xylem area. Application of FA7 led to better results in As and xylem conduits.