Sustainable Nitrogen Management in Olive Cultivation Through Chabazite-Zeolite Amendment: Growth Response, Yields and Life Cycle Assessment

Improving nitrogen (N) use efficiency in olive cultivation is essential to address the environmental burden of N fertilizers, whose recovery efficiency rarely exceeds 55%. This study evaluates the agronomic and environmental performance of chabazite-rich zeolite as a soil amendment to enable 50% N-fertilizer reduction in olive growing. A seven-year field experiment (2017–2023) was conducted at two sites in Emilia-Romagna (Italy)—one irrigated (Brisighella) and one rainfed (Bertinoro)—comparing four autochthonous varieties under zeolite amendment (ZEO, 50% N) versus conventional fertilization (CNT, 100% N). Vegetative growth, productive parameters, oil quality and environmental impacts (Life Cycle Assessment, ISO 14040/44) were monitored. Under irrigation, ZEO maintained vegetative and productive equivalence with CNT, sustaining commercially viable yields (0.5–2.3 t ha−1). Under rainfed conditions, variety-specific responses emerged: Colombina exhibited 126.2% greater trunk diameter and near-universal fruiting competence (88.9% vs. 29–35% productive plants) under ZEO, while Capolga showed treatment convergence. LCA revealed higher per-unit environmental impacts for ZEO during early orchard phases due to front-loaded extraction burdens, progressively offset by annual N-input reductions. These findings demonstrate that zeolite amendment enables agronomically viable 50% N-fertilizer reduction, with efficacy modulated by water regime and genotype.