Biodegradable Mulch Thickness and Color Effects: Multi-Environment Assessment for Optimizing Processing Tomato Yield and Performance

The Mediterranean Basin faces increasing risks from extreme weather events, particularly heat stress, which severely threatens the productivity of sensitive crops, like processing tomato (Solanum lycopersicum L.). This study evaluated the agronomic, physiological, quality, and economic performance of using Mater-Bi®-based biodegradable mulch films—varying in color (black and White/Black) and thickness (12 µm and 15 µm)—in two distinct Southern Italian pedoclimatic sites: Sicily and Campania. The aim was to define site-specific optimization strategies by comparing three biodegradable mulch film treatments, 12 µm (BDM12), 15 µm (BDM15), and Black/White (BDBW), against bare soil (BS). The results confirmed that biodegradable mulching enhances plant physiological status, such as chlorophyll and nitrogen balance index (NBI), and marketable yield compared to BS. The effectiveness of the films depended significantly on the environment. In Sicily, the BDBW (White/Black) film provided the maximum marketable yield (804.7 q ha−1), confirming its crucial role in mitigating high soil temperatures through radiation reflection. Conversely, in the more favorable Campanian environment, the thicker black film (BDN15) achieved the highest yield (867.3 q ha−1), indicating that microclimate stability is prioritized over heat mitigation under optimal conditions. Quality analysis showed high variability; while the Sicilian site generally favored color and antioxidant capacity, total soluble solids (°Brix) exhibited a trade-off. BDBW achieved the highest °Brix (6.1) in Sicily, while BS yielded the highest (6.03) in Campania, suggesting that slight water stress can concentrate sugars at the expense of total yield. The economic analysis demonstrated that the °Brix increase achieved with biodegradable films provided a net additional economic return superior to BS in both sites (up to +52.92% with BDBW). These findings suggest that the adoption of biodegradable mulching represents a key strategy for the sustainable intensification of processing tomato. Future cultivation strategies must mandatorily integrate the personalized selection of film color and thickness as a key element to synergistically maximize yield, quality, and economic return, tailored to the specific pedoclimatic conditions of each production site.