Enhancing sustainability of a processing tomato cultivation system by using bioactive compost teas

• Compost teas had positive effects on health and yields of tomato.
• Compost tea-spraying improve sustainability of disease management.
• Suppressive/stimulative mechanisms underlying compost tea efficacy are proposed.
• Organic treatments supplied microbes and nutrients to plants.
• Bioactive humic C-types may be involved in hormone-like properties of teas.

Compost teas are compost-derived liquid products that may potentially induce positive effects on treated crops, including disease suppressiveness and biostimulation of the overall improved plant status. In this work four teas, produced from agricultural and municipal waste compost, were applied in a processing tomato cropping system to gain sustainable diseases management. Field trials showed that teas had a positive impact on health and vegetative status of the plants subjected to natural leaf blights, and induced significant increases of yields. The occurrence of combined suppressive and biostimulation mechanisms, sustained by microbial communities, nutrients supply and carbon-based bioactive compounds, was assumed to underlie the observed effects of tea on plants. Furthermore, NMR spectra suggested that the supramolecular organic structures contained in compost teas may be involved in the inductive processes of biostimulation, including an auxin-like activity. Molecular profiles of organic matter dissolved in teas indicated that the interaction between hydrophobic groups and polysaccharidic moieties could be related to vegetative responses of treated plants. This study provides new insights concerning the comprehension of the overall functionality of compost teas and their applicability in a timely disease management of crop systems.