Almond shell biochar: characterization and application in soilless cultivation of Eruca sativa

Soilless cultivation currently competes with open-field production. Although the substrate used is generally perlite, there is interest in looking for new materials that can help growers produce healthy plants with sustainable practices. Among these new materials, biochar could be an alternative, as it has numerous benefits for substrate health, water retention, carbon sequestration, and nutrient supply. Thus, the objective of this work was to evaluate the effects of almond shell biochar (ASB) addition to perlite on the physicochemical properties of this substrate and its influence on the agronomic characteristics of arugula ( Eruca sativa ) cultivation. Two variables were included: (a) percentage of ASB added (0, 5, 10, and 15% w/w ASB/perlite) and (b) compost tea for irrigation (0 and 5 g/L of water). In addition, correlations were proposed to describe the dependence of the agronomic variables on the percentage of ASB added and the type of irrigation solution used. The results demonstrated that adding 10% of ASB and irrigating with water improved the characteristics of arugula plants compared with controls, while compost tea did not influence the agronomic parameters evaluated. The models proposed showed that the agronomic variables depend on the percentage of biochar added and compost tea ( R 2 ≥ 0.90). The interaction between both variables was negative. ASB addition improved soilless arugula cultivation, compared to the use of perlite alone. Moreover, the use of almond shell as a raw material in the pyrolysis process to obtain biochar reduces the environmental impact, tending to the circular economy concept. Graphical Abstract