Nowadays, modern agriculture looks for valid, sustainable, and green alternatives that are able to improve and maintain soil quality and fertility over time. Recycling organic waste as fertilizer is one of the strategies for sustainable production. Recently, the use of new products derived from compost, such as compost tea (CT), is increasing due to their positive effects on crops. This perspective wants to give an updated shot at the effect of compost tea in horticulture. In addition to the classification of compost tea, with a focus on production procedures and composition, the possible effects they have both on the control of phytopathogens in horticulture and the influence they can have on the content of bioactive molecules and nutrients were highlighted. It is interesting to note that compost teas can have an effect on the final content of micro and macronutrients, thus improving the nutritional qualities and also increasing the content of bioactive compounds that may play a role in maintaining and improving human health. The combined use of compost tea with other treatments is being explored as a promising and innovative direction.

It is desirable to find and evaluate innovative sustainable products guaranteeing and increasing the quality and productivity of radish (Raphanus sativus). Compost tea (CT) represents a natural organic preparation providing benefits to the soil–plant system, including a biostimulant action against climate change. Therefore, we evaluated whether CT can influence radish nutraceutical properties and its primary metabolism. In particular, the roots resulting from CT treatment were examined via conventional (total antioxidant and phenol contents) and spectroscopic techniques (high-resolution NMR and NIR) and compared with controls. It was proved that CT exerted a positive effect on the radish quality, which led to a significantly larger size in those treated (TRT), accompanied by higher contents of total antioxidants and phenols. The assignment of ¹H and ¹³C signals in the NMR spectra allowed the delineation of the NMR fingerprint of the radish primary metabolome, which was processed by multivariate statistical analyses (PCA, PLS-DA, and heatmap clusterisation). TRT metabolites exhibited a peculiar profile, characterized by higher levels of glutamine and malic acid, along with lower levels of glucose, fructose, sucrose, lactic acid, and tryptophan. NIR spectroscopy also identified a recognisable profile in TRT, confirming its role as an alternative and accessible technique to appreciate the organic treatment’s effects on radish.