Biodegradable mulches vs. bare soil in processing tomato improves yield, quality and water productivity under Mediterranean conditions

Three mulching treatments: a paper mulch (PPR) and two biodegradable films (BM1, starch-polymer blend; BM2, copolyester), were compared with bare soil (BS, control). Soil volumetric water content and soil temperature were monitored to schedule irrigation and restore field capacity. Mulching, regardless of type, increased commercial yield in both years: +48% in 2024 and +24% in 2025 compared to BS, mainly due to higher fruit number. Mulched fruits showed greater firmness and higher °Brix values (+3–9%), although the latter was statistically significant only in the second year. Biodegradable films significantly increased ascorbic acid content (+46% vs. PPR), while PPR, due to its cooling effect, promoted a statistically significant lycopene (+52%) and carotenoids (+24%) content. Nitrogen content of fruits was lower under PPR (−26% in 2024; −3.6% in 2025). Moreover, mulching reduced water volumes and improved WPc, particularly in 2024 (PPR: 83.78 vs. BS: 48.80 kg m-3). Despite lower overall WPc in 2025, mulched plots maintained more stable efficiency. Biodegradable mulches could represent a sustainable alternative to polyethylene for Mediterranean processing tomato cultivation.