The invention relates to a non-toxic composition prepared from agricultural waste, including steps of a) hydrolysing the plant matter in acidic conditions； b) nitrating the released phenolic compounds； c) stimulating the coupling between the phenolic compounds which are nitrated or not； d) insolubilizing and separating the coupled compounds； and e) drying the precipitated insoluble solids. The resulting composition, when applied to plants, has phytoregulating properties that induces favorable metabolic and physiological changes which promote increases in the mass of the roots and the photosynthetic capacity, in the resistance to biotic factors, in the tolerance to abiotic stress factors and/or in the productivity of the crops.
