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

Agriculture consumes 70% of global freshwater, and rising food demand by 2050 will further strain these resources. Mulching can improve water productivity (WP) by reducing evaporation and stabilizing the soil microclimate. This study evaluated the effects of biodegradable mulch on irrigation efficiency, yield, and quality of processing tomato ( Solanum lycopersicum L.) under Mediterranean open-field conditions. Trial was conducted over two consecutive spring–summer seasons (2024–2025), at Portici, Southern Italy. 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 WP c , particularly in 2024 (PPR: 83.78 vs. BS: 48.80 kg m -3 ). Despite lower overall WP c in 2025, mulched plots maintained more stable efficiency. Biodegradable mulches could represent a sustainable alternative to polyethylene for Mediterranean processing tomato cultivation.