Foliar Application of a Biostimulant Based on Fermented Pomegranate Waste Increases Tomato Yield in Greenhouse

The use of biostimulants can help to mitigate the conditions of biotic and abiotic stresses in crops by enhancing the crop yield and product nutrients. The novelty of this research was to produce a biostimulant for the tomato cultivation through fermentation of pomegranate waste, evaluating in the crop the effect on the growth, development, and quality of tomato fruits. Pomegranate bagasse was used as a substrate during the liquid fermentation using <i>Aspergillus niger</i> M4 strain. Three applications of fermented extract were made in three phenological crop stages for each of the four different treatments. The biotechnological process allowed the transformation of pomegranate residues, increasing the content of antioxidant activity and catechin in 467% and 315%, respectively. The fermentation enabled the mineral content modification, such as the condensed tannins, zinc, magnesium, and antioxidant capacity. By applying the fermented extract of pomegranate, an increase of 34% in crop yield and a 32% in the lycopene content in tomato fruit was obtained. The use of a fermentative process enables the pomegranate waste mineral modification, enhancing the biostimulant capacity of pomegranate residues. The foliar application of a raw pomegranate fermented extract increases the crop yield and nutritional quality of the tomato fruits.