Biologically activated biochars enhance soil chemical–biological functioning and Lolium perenne yield in contrasting soils
Abstract
Soil responses to biochar depend not only on feedstock origin but also on interactions between biochar architecture, biological activation, and soil mineral composition. This study evaluated how biological activation pathways modify the chemical and biochemical responses of two contrasting soils amended with biochars derived from rice hulls and cherry pruning residues. Biochars were biologically activated through Lumbricus terrestris , vermicomposting with Eisenia fetida , and bokashi fermentation, then applied at rates ranging from 0.5 to 2.0% (w/w) to a volcanic Andisol and a Mediterranean Alfisol cultivated with Lolium perenne L. under controlled conditions. Soil chemical properties, forage yield, and enzyme activities associated with C, N, and P cycling were evaluated as indicators of soil functionality. Responses differed markedly according to soil type and activation strategy. In Andisol, bokashi-activated cherry pruning biochar applied at 1.5% promoted the highest forage yield, together with greater total N retention, improved nutrient availability, and differentiated enzymatic responses. These responses were particularly evident in treatments receiving the highly porous and chemically reactive cherry pruning biochar. In Alfisol, biologically activated biochar mitigated SOC depletion and stimulated nutrient-related enzymatic activity, although responses remained more variable than in Andisol. Principal component analysis explained 88.6% of the total variance, while Pearson correlation analysis revealed clear associations between enzymatic responses, nutrient dynamics, and soil physicochemical context. The results indicate that the effectiveness of biologically activated biochars depends on the interaction between pore architecture, surface reactivity, and soil type, highlighting the need for soil-specific biochar design strategies to improve soil functionality and agricultural sustainability.