Herbicide application increases nitrogen (15N) exudation and root detachment of Brachiaria decumbens Stapf

Current research shows that glyphosate herbicides can increase nitrogen exudation by plant roots and, as a consequence, favor pathogenic fungal colonization in soil. In Brazilian agroecosystems, the main herbicides used in conservationist systems for glyphosate substitution are glufosinate and paraquat. However, no studies have been developed that to evaluate the effects of these herbicides on nitrogen exudation by roots. This work was carried out with the objective of evaluating the exudation of nitrogen (N-15) compounds and root detachment after the application of glyphosate, glufosinate-ammonium or paraquat on Brachiaria decumbens Stapf. The ammonium concentration in the plant's tissues and the nitrogen (N-15) recovery in the plant-solution system were also evaluated. The nitrogen left by the soil-solution system and the ammonium concentration in the plant's tissues were increased after glyphosate or glufosinate application, but they were not modified by paraquat. Nitrogen compound exudation and root detachment were increased by the desiccation of Brachiaria decumbens Stapf by the use of the following herbicides: glyphosate, glufosinate-ammonium and paraquat. This increase demonstrated that the nitrogen exudation was not affected by a particular herbicide's mode of action.