Vegetal-protein hydrolysates based microgranule enhances growth, mineral content, and quality traits of vegetable transplants

The urgent need to increase sustainable crop production has pushed the agricultural sector towards methods based on natural products such as biostimulants. The nursery industry holds strategic importance for modern horticulture because only “high quality” seedlings can guarantee productive success. The aim of our research was to assess the effects of a microgranule plant-derived biostimulant added to the transplants’ substrate. Biometric parameters, mineral composition, total chlorophylls, carotenoids, and total phenols content of eggplant (Solanum melongena L., cv. Mirabelle F1), pepper (Capsicum annuum L., cv. Tarquinio F1), and tomato (Solanum lycopersicum L., cv. Taylor F1) at four different biostimulant doses (0.5, 1, 2, and 4 g L−1) were evaluated. Compared to the untreated control, the use of the highest dose of microgranule biostimulant (4.0 g L−1) increased shoot dry weight by 73%, 61%, and 33% and root dry weight by 37%, 34%, 36%, for eggplant, pepper, and tomato, respectively. Similarly, the nitrogen and potassium contents of eggplant, pepper, and tomato plants were positively affected by biostimulant application. Total chlorophylls content and carotenoids were significantly affected only in tomato leaves with the 2.0 and 4.0 g L−1 doses while no significant differences for total phenols were recorded in transplant leaves of tested vegetable crops. Chlorophyll a/b decreased in eggplant and pepper with increasing microgranular-based PHs rates, indicating a greater accumulation of chlorophyll b than chlorophyll a. Our results show that microgranule biostimulant application directly mixed in the substrate can improve the quali-quantitative traits of nursery seedlings while reducing the excessive use of fertilizers and concomitantly producing vigorous seedlings potentially capable of overcoming easily transplant stress.