A review of silicon-rich biochar for ecological insect pest management through enhanced plant resistance and multi-trophic interactions
Silicon-rich biochar (Sichar) is increasingly evaluated as a functional option in sustainable agriculture by aligning carbon storage pathways with ecological insect pest management frameworks. This review synthesizes the investigated mechanisms through which Sichar modifies plant defenses against insect herbivores across diverse ecosystems. When derived from high-silicon biomass, Sichar applications can increase the concentration of available silicic acid in the soil solution, which frequently correlates with the deposition of structural opaline silica barriers within plant vegetative tissues to physically impede specific chewing and piercing-sucking insect pests. Beyond acting as a mechanical barrier, soil-applied Sichar has been shown to alter systemic defenses by modulating endogenous phytohormone-signaling pathways, particularly those mediated by jasmonic acid and salicylic acid, potentially upregulating the biosynthesis of specific defense-related secondary metabolites. These biochemical shifts influence host-plant resistance traits and may simultaneously affect the recruitment of natural enemies via modified emissions of volatile organic compounds that mediate tritrophic interactions. Furthermore, Sichar amendments modify soil physicochemical properties and nutrient cycling, creating a rhizosphere environment that can support beneficial soil microbial communities and maintain baseline plant vigor metrics. Although Sichar assists in managing specific synthetic pesticide residues through surface adsorption or microbial-mediated degradation pathways, its variable influence on non-target beneficial organisms and localized soil moisture dynamics requires systematic evaluation. Optimizing pyrolysis parameters and field application strategies allows Sichar to function as an integrated component of integrated pest management frameworks that align with the principles of a circular economy. This synthesis establishes an evidence-based framework for future empirical research aimed at quantifying and validating the protective parameters of Sichar in diversified cropping systems. Silicon-rich biochar (Sichar) soil deposition modifies structural opaline barriers and alters endogenous phytohormone-signaling pathways, which can suppress the feeding performance and population growth parameters of specific chewing and piercing-sucking insect feeding guilds. Rhizosphere amendments utilizing Sichar influence insect herbivore development, which is frequently associated with delayed nymphal and larval maturation, reduced fecundity, and a reduction in observed crop tissue damage. Sichar serves as an ecologically integrated soil conditioner within targeted integrated pest management frameworks, offering a potential cultural mechanism to decrease reliance on synthetic chemical insecticides.