Nitrogen(15N) loss in the soil-plant system after herbicide application on Pennisetum glaucum

In direct sowing, desiccation of the cover crops with herbicides can affect N availability in agroecosystems, reducing N use efficiency by the crop in succession. In this sense, the objective of the study was to evaluate nitrogen losses in the soil-plant system after application of the herbicides glyphosate and glufosinate-ammonium on pearl millet [Pennisetum glaucum (L.) R. Brown, var. ADR500]. Plants were grown in a sandy soil, fertilized with N-15 ammonium sulfate, at N dose of 135.7 mg kg(-1). After herbicide application, the N distribution within the plant was changed, with an observed N reduction in leaves and increased N in stalks. The glyphosate and glufosinate reduced, by 25 and 30%, respectively, the amount of N in plant tissues and increased by 3.0 g m(-2) the losses in the soil-plant system of the N provided from the fertilizer. This information can be useful in preparing management strategies that will provide greater nitrogen fertilization effectiveness and, consequently, smaller environmental impacts from the use of nitrogen fertilizers and herbicides.