Biochar Improves Plant Vigor and Defense Response to Green Peach Aphid Myzus persicae in Hydroponic Lettuce ( Lactuca sativa )

ABSTRACT Biochar (BC) is increasingly recognized as a sustainable agricultural amendment to improve soil health, promote plant growth, and suppress insect pests. While its application has been extensively refined in conventional soil‐based agroecosystems, its performance in hydroponics, particularly in liquid formulations remain largely unexplored. The variability in BC feedstocks, pyrolysis parameters, delivery methods and application rates demands optimization to maximize benefits while avoiding unintended effects on plants and beneficial organisms. In this study, we evaluated the concentration dependent effects of pine‐derived liquid BC applied to a rockwool based hydroponic lettuce ( Lactuca sativa ) system under green peach aphid (GPA) ( Myzus persicae ) herbivory. After germination in water for 14 days, the seedlings were subjected to BC sub‐irrigation at 0% (control), 1%, 5%, and 10% BC concentrations and evaluated for plant growth parameters, physiological traits, and aphid performance. Our results show that a single application of liquid BC amendment of 5% resulted in enhanced early seedling vigor when compared to other concentrations and also adversely affected aphid performance. Overall, the findings from this study collectively suggest that 5% BC mediated substrate amendment represents an optimal concentration for managing GPAs in hydroponic lettuce production. The aphids exhibited reduced performance and showed a clear preference against plants that received 5% BC treatment. The results from this study are exploratory and demonstrate that the effects of the pine‐BC observed here are concentration dependent, within a single substrate and plant species underscoring the importance of systematic optimization of BC use to fully realize it's potential for sustainable crop production and pest control.