The invention provides a copper-based liquid formulation for enhancing self-defence in plants comprising between 10% and 15% sodium lignosulfonate, between 15% and 25% copper sulfate, between 0.20% and 0.40% MSB and between 1.30% and 1.75% plant-derived free amino acids, with the remainder being water, expressed as weight percentages with respect to 100% of the final liquid formulation by weight, and the application thereof in fertigation, drip or spray irrigation, or by spreading same in areas close to the plant by flood irrigation.
