Processing tomato - RDI x Biodegradable mulching film

Italy is the third largest producer of processing tomatoes (Solanum lycopersicum L.) worldwide. Tomato production is projected to be considerably affected by climate change, especially in drought-prone regions where maximizing water use efficiency is essential. A two-year on-farm experiment was conducted to compare full irrigation (T1) with two water-saving irrigation strategies: T2 (regulated deficit irrigation, RDI) and T3 (RDI combined with soil-biodegradable mulch film). The experiment was conducted at two representative sites in southern Italy, where yield performance, sustainability, and fruit quality were assessed. T2 resulted in 31 % water savings and maintained comparable yields, increasing irrigation (+44 %) and economic (+56 %) water productivities with respect to T1. Nevertheless, the accelerated crop cycle observed in T2 reduced the leaf coverage of fruit, leading to a higher number of sun-scalded fruits and decreased lycopene content at harvest. The negative effects of RDI were partially mitigated by combining it with soil-biodegradable mulch film (T3), which improved the soluble solid content (+4 %), marketable (+23 %) and Brix (+28 %) yields, and irrigation (+71 %) and economic (+78 %) water productivities compared with T1. Metabolic profiling further highlighted that T3 increased key stress-related metabolites, including alanine (+50 %), glycine (+31 %), and proline (+44 %), indicating enhanced metabolic adaptation to water stress. The increase in proline, a crucial osmolyte and antioxidant, suggests improved nitrogen use efficiency and overall metabolic resilience under water-deficient conditions. Based on these findings, T3 is recommended as a valuable practice for improving yield and sustainability, while maintaining fruit quality in drought-prone areas.