Enhancing Tomato Growth and Quality Under Deficit Irrigation with Silicon Application

This study aimed to evaluate the effect of two irrigation systems (deficit irrigation (DI)-70% of field capacity-and full irrigation (FI)-100% of field capacity) and a biostimulant formulation (silicon (Si) and calcium (Ca) at four different rates) on the chemical composition and fruit quality of greenhouse-grown tomatoes. Deficit irrigation and biostimulant application influenced the proximate composition of tomato fruits. Fructose and glucose were the main soluble sugars, while malic and citric acids were the predominant organic acids. Free sugar and organic acid content increased under DI and biostimulant applications. In contrast, deficit irrigation combined with biostimulant application decreased alpha-tocopherol levels. In terms of carotenoids, lycopene and beta-carotene concentrations were higher under full irrigation. The main fatty acids were palmitic (C16:0) and linoleic (C18:2n6) acids, with saturated (SFA) and polyunsaturated (PUFA) fatty acids being the main classes. Moreover, biostimulant applications reduced the total phenolic content regardless of the irrigation regime, whereas the flavonoid content increased when biostimulants were applied under FI conditions. Regarding antioxidant activity (assessed by TBARS and OxHLIA assays), a variable response to irrigation and biostimulant application was observed. In conclusion, the application of Si and Ca under DI showed promising results in terms of yield and quality of tomato fruit and it could be considered a sustainable strategy to mitigate adverse effects of climate change on horticultural crops.