Unraveling the effect of phenolic extract derived from olive mill solid wastes on agro-physiological and biochemical traits of pomegranate and its associated rhizospheric soil properties

Agricultural waste management poses a significant challenge in circular economy strategies. Olive mill wastes (OMW) contain valuable biomolecules, especially phenolic compounds, with significant agricultural potential. Our study evaluate the effects of phenolic extract (PE) derived from olive mill solid wastes (OMSW) on pomegranate agro-physiological and biochemical responses, as well as soil-related attributes. Pomegranate plants were treated with PE at doses of 100 ppm and 200 ppm via foliar spray (L100 and L200) and soil application (S100 and S200). Results showed increased biomass with PE treatments, especially with soil application (S100 and S200). Proline and soluble sugar accumulation in leaves suggested plant adaptation to PE with low-level stress. Additionally, PE application reduced malondialdehyde (MDA) and hydrogen peroxide (H2O2) contents. Higher doses of PE (S200) significantly improved net photosynthesis (Pn), transpiration rate (E), water use efficiency (WUEi), and photosynthetic efficiency (fv/fm and PIabs). Furthermore, PE treatments enhanced levels of chlorophylls, carotenoids, polyphenols, flavonoids, and antioxidant activity. Soil application of PE also increased soil enzyme activities and microbial population. Our findings suggest the beneficial impact of PE application on pomegranate agro-physiological responses, laying the groundwork for further research across various plant species and soil types to introduce nutrient-enriched PE as an eco-friendly biostimulant. Olive mill solid wastes (OMSW) generated from olive oil extraction industry pose serious environmental problems if not managed properly. However, these residues constitute a valuable source of natural biophenols. Our study presents a pathway for valorizing this waste by producing a biostimulant from a polyphenol-enriched extract derived from OMSW, providing a sustainable alternative to harmful agrochemicals. Accordingly, this approach aligns with circular economy principles and provides a sustainable solution for agro-industrial sectors.