Losses of 15N-nitrogen by plant-soil system after herbicide application on black oat

Recent studies have demonstrated that the use of glyphosate or glufosinate-ammonium herbicides for some cover crop desiccation in conservationist systems could favor nitrogen (N) losses from the soil-plant system. In this context, the objective of this study was to evaluate the losses of N by the plant-soil system after the desiccation of black oat (Avena strigosa Schreb.) with the application of herbicides glyphosate, glufosinate-ammonium, or paraquat. Two greenhouse experiments were implemented using black oat plants fertilized with labeled (N-15) ammonium nitrogen, and the N loss of the plant-soil system was quantified. The desiccation of black oat with glyphosate caused a reduction in root dry mass by approximately 60% in both experiments. The glyphosate and glufosinate-ammonium reduced the amount of N present in the aboveground portion; however, the paraquat herbicide did not modify it. None of the herbicides applied affected N losses in the black oat plant-soil system. However, 5-15% of the N applied as fertilizer was lost up to harvest. The results suggest that black oat can be used as a cover crop in direct sowing in order to avoid nitrogen losses in the soil-plant system.