Trichoderma-Activated Granulated Digestate as an Alternative to Chemical Fertilization: Effects on Tomato Yield and Quality, and Soil Rhizospheric Communities

The use of synthetic fertilizers is always more economically and environmentally unsustainable. It is necessary to improve current agricultural practices. Bioactivated fertilizers are a promising solution to enhance digestate solid fraction’s fertilizing properties with an ad hoc microbial consortium and reach yields comparable to chemical fertilization (CF), thus combining circular economy with an upgraded organic agriculture. This study designed a new granulated formulation, obtained using a vacuum drying process at the industrial level, for an improved Trichoderma-activated digestate’s solid fraction. This granulation aimed to improve both management operations and Trichoderma activity. After a greenhouse experimentation, yields obtained from the activated digestate (56 ± 7 g FW plant–1) were similar to the one obtained with CF (62 ± 9 g FW plant–1). Additionally, the bioactivated digestate gave yield production that were 21–30% higher yield than that of digestate alone. Microbial activation further led to higher nutritional values with an increment in the lycopene content between 8.8% and 15.8%. A metagenomic analysis further highlighted the persistence of Trichoderma in the tomato rhizosphere and its ability to establish positive interactions with other beneficial rhizospheric microorganisms. Activated digestate showed its potential to substitute CF, while granulation resulted in a functional formulation to convey this product