Title : Botanical extracts for sustainable nitrogen management in melon cropping systems, southern Tunisia
Abstract:
Reducing nitrogen (N) fertilizer inputs is a major challenge for sustainable agriculture in Mediterranean agroecosystems, where excessive N application increases environmental risks. This study evaluated whether botanical extracts can compensate for further N reductions while maintaining crop productivity and quality. The experiment was conducted on melon (Cucumis melo L.) in southern Tunisia (Limaoua, Gabès). The control treatment (N1) already represented an optimized fertilization regime with a 30% reduction from the total crop N requirement. Two additional restriction levels were applied relative to this control: 15% (N2) and 30% (N3). Under N2 and N3, two botanical extracts (Nemagold and Fitomare) were applied and compared to the control. Further N reduction significantly affected fruit growth and yield, with the strongest declines observed under N3. However, under N2, both botanical extracts maintained fruit length, width, and seed cavity dimensions at levels statistically comparable to the control. Total yield under N2 with botanical extracts (34.0–34.6 t ha-¹) remained close to the control (38.5 t ha-¹). In contrast, N3 caused a significant yield reduction, particularly with Nemagold, while Fitomare partially mitigated yield losses by maintaining higher pulp and skin weights. Quality responses varied among treatments. Fitomare under N2 significantly increased soluble solids content and dry matter compared to the control, indicating improved fruit quality despite reduced N input. Reduced N treatments showed lower soil and leaf nitrate accumulation and higher leaf C/N ratios, suggesting improved nitrogen use efficiency. These results indicate that, starting from an already optimized N regime, an additional 15% reduction in nitrogen fertilization can be effectively compensated by botanical extracts—especially Fitomare—without major yield penalties and with improved quality and nitrogen efficiency.
