Improving tomato productivity, quality and drought resilience with an innovative organo-mineral amendment

In arid regions, water scarcity is a critical limitation to tomato growth and fruit quality, emphasising the need for sustainable practices that enhance resource efficiency. The combined use of compost and ferrous slag (CS) in open-field tomato cultivation remains largely unexplored. This study was conducted in the Mediterranean region to evaluate the effects of compost, ferrous slag, and their mixture on tomato (Solanum lycopersicum L.) productivity and nutritional quality under full and deficit irrigation. Results revealed that in comparison to the control plants, tomato yield decreased by 36% and 41% in the first and second seasons, respectively, by deficit irrigation (DI). However, yields greatly increased by 40% and 57% during the two seasons when DI was combined with the CS amendment. Comparing DI combined with CS to the control, the combined amendment consistently enhanced fruit quality by increasing soluble sugars, protein concentration, carotenoids, and lycopene. These improvements, together with the sustained tomato productivity under DI, demonstrate that the CS combination effectively mitigates the adverse effects of water stress and represents a sustainable organo-mineral strategy for improving crop performance and fruit nutritional quality in water-limited agroecosystems.