Trick of the Trade: Unveiling the Importance of Feedstock Chemistry in Trichoderma-Organic Amendments-Based Bio-Stimulants

Abstract

We investigated the effect of Trichoderma harzianum in combination with biochar or other organic feedstocks, i.e., fish meal, Medicago, and maize straw, on the growth of Lens culinaris, Zea mays, Oryza sativa, and Glycine max. Biochar and other organic feedstocks were characterized by 13C-CPMAS NMR spectroscopy. Fish and Medicago had low C/N and high N content, while biochar, maize, and AC (Activated Carbon) had high C/N. pH ranged from 9.38 for biochar to 5.67 for AC. 13C-CPMAS NMR showed large chemical changes in organic mixtures leading to aromatic C-type enrichment in the presence of biochar or AC. Biochar and organic feedstocks inoculated with T. harzianum showed different effects, ranging from inhibition to crop stimulation. Overall, out of 88 cases, T. harzianum inoculum had a positive effect on root length in 46 cases (52.2%). The effect of fungal inoculum was particularly positive when combined with AC or biochar and when non-pyrogenic amendments were present. In contrast, a negative effect was observed when T. harzianum was inoculated with N-rich non-stabilized organic amendments. Further research is needed to identify the specific mechanisms underlying the inhibitory and bio-stimulatory effects of Trichoderma mixtures with organic amendment for the right combinations of raw materials that maximize crop productivity.