Invasive species control management involves a large amount of plant material. The present work evaluated the allelopathic potential of the invasive species Ulex europaeus L. (Fabaceae) or ‘Gorse’ and its possible use as a bioherbicide, taking advantage of the extracted plant material after control measures, particularly needed in invaded areas. Specifically, we investigated the efficacy of dried plant material from U. europaeus in the control of the adventitious plants, Lolium multiflorum Lam. and Lolium rigidum Gaud., using the Avena sativa L. crop as a case study. We only used vegetative plant parts because it is essential to avoid the dispersion of U. europaeus with its use, especially in invaded areas. A greenhouse pot experiment was conducted, using activated carbon (AC). The target species (L. multiflorum, L. rigidum and A. sativa) were subjected to a mixture of organic substrate with U. europaeus mulch applied pre-emergence and a subsequent application of aqueous extracts from the mulch. Emergence, height and biomass of the target species were determined. After 2 months, we also tested a possible legacy effect of the substrate on the germination of the target species. We noticed a negative effect of U. europaeus mulch on the emergence of L. rigidum, which can be attributable to the allelopathic compounds released from U. europaeus mulch because the effect was non-significant in presence of AC. Conversely, no effect on L. multiflorum or A. sativa was produced by mulch treatments. Nevertheless, the combination of U. europaeus mulch and its extracts demonstrated a phytotoxic effect on the biomass of the crop species A. sativa, and a fertilizing effect on the weeds L. multiflorum and L. rigidum, which is why this use is discouraged. With our results we cannot recommend the use of U. europaeus as a bioherbicide in oat crops, but this study emphasizes the capability of U. europaeus to structure plant communities through the chemic- and bio-properties of its tissues that modifies the soil environment.
