Impacts of Conventional and Agri-Food Waste-Derived Fertilizers on Durum Wheat Yield, Grain Quality, and Soil Health: A Two-Year Field Study in Greece and Southern Italy

Background: In the context of climate change and the European Green Deal, sustainable fertilization practices are essential to enhance crop yield and soil health. Organic fertiliz-ers from agro-industrial waste are gaining attention as alternatives to synthetic inputs. This study evaluates a novel fertilizer (RecOrgFert), composed of sulfur bentonite and cit-rus-processing residues. Methods: A two-year field trial was carried out in Central Mace-donia (Northern Greece) and Apulia (Southern Italy) using a randomized complete block design with four treatments: unfertilized control, mineral NPK (15-15-15), horse manure, and RecOrgFert. Soil chemical and biological properties, plant growth parameters, yield components, and grain quality indicators were assessed. Results: RecOrgFert improved soil organic matter (+22–30%), cation exchange capacity, and enzymatic activity. Wheat grain showed higher protein content (up to 15.2%), antioxidant activity (DPPH > 37%, ABTS+ > 26%), and increased phenolic and flavonoid levels compared to other treatments. These benefits were consistent across both sites and years. Conclusion: RecOrgFert en-hanced soil fertility and wheat quality while maintaining yields comparable to mineral fertilizers. Its sulfur and citrus-derived composition supports nutrient cycling and bioac-tivity, aligning with EU strategies for sustainable agriculture. RecOrgFert offers a viable, circular solution for Mediterranean cereal systems, further contributing to circular econo-my implementation plans