Valorization of grape pomace through melanin extraction and its biostimulant effects on yield and development of winter barley

Recent advancements in agricultural research have focused on the development of plant-and animal-derived substances with biostimulant properties.Among these, melanin extracted from grape pomace has garnered significant attention due to its diverse biological activities and promising potential as an agricultural biostimulant.This study aims to identify the optimal technological parameters for extracting natural melanin from plant-based industrial waste.Additionally, it seeks to determine the optimal application rate of the extracted melanin and evaluate its effects on the growth and yield parameters of winter barley (Hordeum vulgare L.) Melanin content was determined using gravimetric and spectroscopic methods.Field trials followed the Community Plant Variety Office (CPVO) distinctness, uniformity and stability (DUS) testing protocol for barley.The optimal conditions for melanin extraction from grape pomace were determined to be a solid-toliquid ratio of 1:14, a 0.4 M NaOH solution concentration, an extraction temperature of 60 C, and a duration of 2.5 h.Under these conditions, the melanin yield reached 90% of the initial content present in the raw material.Field experiments were conducted from 2021 to 2024 under irrigated conditions on brown semidesert soils, using a completely randomized design with three replicates.Melanin acts as a biostimulant for winter barley when applied at a concentration of 0.028% for seed treatment and 0.014% for three foliar applications, starting at the stem extension stage and continuing weekly through the heading stage.The results demonstrate that melanin enhances seed germination by 7.6% in the field conditions, accelerates plant development, reduces maturation time by 7-11 d, and increases yield by 2.41 t.The incorporation of melanin extract into agricultural systems offers a practical strategy for improving crop productivity, promoting sustainability, and addressing the challenges faced in modern farming.