Impact of Salinity and Biostimulants on Cherry Tomato Yield and Quality

Salt stress causes several detrimental effects on the growth and production of cultivated plants; therefore, scientists have investigated several strategies to mitigate the adverse effects of salt stress, including the application of biostimulants. In our research, we tested four salinity levels of irrigation water (tap water and water at 3.0, 6.0, and 9.0 dS m−1, EC0, EC3, EC6, and EC9, respectively) and two biostimulant applications (untreated plants—Control and plants treated with an extract from seaweed Ascophyllum nodosum—Bio) on a cherry-type tomato. The marketable tomato yield linearly decreased with increasing salinity stress in both treated and untreated plants. However, biostimulant application boosted the production, on average, by 53.2%, significantly impacting only the Control and EC3 treatments. Regarding qualitative traits, no interaction between the factors was detected, except for color parameters. Nonetheless, salinity, particularly in the two less stressed treatments, led to an increase in total soluble solids, firmness, lipophilic antioxidant activity, and ascorbic acid, while the biostimulant improved plant biomass, total soluble solids, firmness, and hydrophilic antioxidant activity. In conclusion, the seaweed extract of Ascophyllum nodosum elicited a beneficial response in tomato plants subjected to low levels of salt stress, as well as in optimal irrigation condition.