Evaluation of Wood Vinegar from the Pyrolysis of Wood Residues of Gmelina arborea and its Application as Herbicide for Weed Control

Wood vinegar (WV) produced via biomass pyrolysis, presents an organic alternative for weed control. This study aimed to: (i) determine the physical properties and elemental composition analysis of WV, and (ii) evaluate the efficacy of WV from wood residues of Gmelina arborea produced with slow pyrolysis to control weeds under a Cupressus lusitanica Christmas tree plantation. WV was dissolved in water at 75% and applied in doses of 1000, 3000 and 5000 L ha^-1, with the synthetic herbicide Basta® (glufosinate-ammonium) as a control. The efficacy of WV on weeds was visually evaluated from 0 (not injury) to 100 (plant death). Treatments with 3000 and 5000 L ha⁻¹ doses caused rapid desiccation of grass and broadleaf weeds, achieving 85 to 88% visual injury. Biomass reduction of 40% can be obtained when WV is applied at high doses (3000 and 5000 L ha^-1) on mature grass-dominated weeds, showing effects comparable to synthetic herbicide. While WV effectively reduced weed biomass, it was insufficient to completely remove mature weeds.