Yeklef NasseraBELGACEM Amel Fatima2026-10-262026-10-262026https://dspace.univ-temouchent.edu.dz/handle/123456789/7764Modern agriculture increasingly relies on sustainable solutions to enhance crop productivity and reduce dependency on chemical fertilizers by recycling organic waste within a circular economy framework. This study aims to evaluate the effect of aqueous extract of Spent Coffee Grounds (SCG) as an organic biostimulant/alternative on the morpho-physiological growth of two major Solanaceae crops: tomato (Solanum lycopersicum, var. Rio Grande) and potato (Solanum tuberosum, var. Spunta ). The field experiment was conducted at Belhadj Bouchaib University of Aïn Témouchent under two different cultivation systems (open field and greenhouse), applying six different aqueous extract concentrations (0%, 5%, 10%, 15%, 20%, and 25%). The results demonstrated a biphasic effect strongly dependent on the applied concentration and the cultivation system: Low to Moderate Concentrations (5% – 10%): Exhibited a significant biostimulant effect, enhancing vegetative growth (stem height and leaf count) while accelerating flowering, fruiting, and fruit ripening in both tomato and potato plants, due to the high content of essential nutrients (Nitrogen, Potassium, Phosphorus) and organic matter in coffee grounds. High Concentrations (15% – 25%): Induced phytotoxicity and osmotic stress caused by the excessive accumulation of secondary metabolites (caffeine, polyphenols, and tannins) and high acidity. This resulted in leaf chlorosis, curling, necrosis, and complete plant mortality (particularly at 25% concentration in greenhouse potatoes). Cultivation System Effect: Plants grown in the open field displayed greater tolerance to high concentrations compared to those in the greenhouse, attributed to natural soil leaching (lessivage) and direct biodegradation of organic compounds. The study recommends avoiding direct application concentrations exceeding 5% to 10% to prevent phytotoxicity, or subjecting spent coffee grounds to prior composting to decompose harmful allelopathic compounds before agricultural use.frSpent Coffee Grounds (SCG)TomatoPotatoBiostimulantsPhytotoxicityOpen FieldGreenhouseThesis