The Action of Plant Protein Hydrolysates, Plant Extracts and Trichoderma atroviride Modulates the Performance of Cherry Tomato Plants Cultivated in a Soilless System

The study and definition of synergistic, additive and antagonistic effects among biostimulants of microbial and nonmicrobial origin represents one of the most interesting prospects for future research. As part of the SO.MI.PR.O.N regional project, we evaluated the effects of the single and combined applications of three different biostimulants [a plant-derived protein hydrolysate (PH), a tropical plant extract (PE) and a microbial biostimulant based on Trichoderma atroviride (Tricho)] on tomatoes (Solanum lycopersicum L.) grown in a protected environment. From the analysis of our results, we observed that compared with the control conditions, all combinations containing Trichoderma atroviride (Tricho+PH, Tricho+PE and Tricho+PE+PH) significantly increased the marketable fruit production. For the latter parameter, the combined application of all tested biostimulants ensured the much-aspired-for synergistic effect. The combined application of all tested biostimulants (Tricho+PE+PH) significantly improved the quality traits (lycopene content, total polyphenols and total soluble solids) of the tomatoes. Although the understanding of the mechanisms activated by the combined application of the different biostimulants still remains complex to define, the results obtained underscore their potential. Not least, it will be necessary to assess the economic feasibility of the combined applications of biostimulants in order to have a more real picture that fully considers the sustainability of this strategy.