Silicon mediated remediation of heavy metal toxicity in crops with global synthesis and delta evidence

Agricultural soils are at risk of heavy metal contamination, which affects crop productivity, food security, and the health of ecosystems worldwide. Traditional remediation methods are expensive, disruptive, and challenging to implement at a field-wide level, underscoring the need to develop sustainable methods. Silicon (Si) has emerged as a potential ameliorative element due to its ability to alleviate heavy metal toxicity through interconnected soil, root, and cellular pathways. This review critically synthesises the existing literature on the mitigating effect of Si on the toxicity of cadmium, arsenic, lead, chromium, and other potentially harmful metalloids in crops. At the soil level, Si lowers metal bioavailability by altering pH, co-precipitating with silicate, and altering metal speciation. At the plant level, Si reinforces the apoplastic barriers of roots, affects the activity of transporters, increases vacuolar fixation, and restricts the movement of toxic substances to edible tissues. However, response levels depend on the crop and soil type, the silicon source, and the application method. Although evidence from rice-based systems is particularly strong, studies from other regions and crop types also indicate broader agronomic potential. The Ganges-Brahmaputra-Meghna (GBM) delta, as a regional case study, demonstrates how silicon can be used to enable crops to withstand a combined heavy metal, salinity, and waterlogging stress under coastal environments. All in all, silicon cannot be regarded as an all-purpose solution but as a situational, nature-related approach to enhancing crop performance and food safety in metal-contaminated agroecosystems.