Strategies for Vegetable Crop Production under Heavy-Metal Stress: A Critical Synthesis of Exposure Control, Rhizosphere Management and Plant-Level Mitigation

Abstract

Vegetable production on land affected by potentially toxic elements creates a dual agronomic problem: plants must maintain growth under metal-induced physiological stress while edible tissues must remain acceptably low in contaminants. These objectives are related but not interchangeable. This critical narrative review evaluates strategies for raising vegetable crops under heavy-metal stress, with particular emphasis on cadmium because vegetable-specific evidence is most developed for this element, while also integrating evidence for lead, arsenic, copper, zinc and mixed contamination. Literature published from 1 January 2000 to 13 June 2026 was considered, with selective inclusion of foundational earlier work. The evidence indicates that the most defensible management hierarchy begins with exposure prevention and source control, followed by crop and cultivar choice, rootstock-mediated exclusion, rhizosphere manipulation, and carefully selected plant-directed or biological interventions. Soil pH, organic matter, cation exchange processes, metal speciation and competing ions strongly modify root exposure; consequently, amendments such as biochar, mineral sorbents, hydroxyapatite, lime and calcium-containing materials can reduce phytoavailability, but their performance is highly soil- and material-dependent. Silicon, selenium, fulvic substances, biopolymers and microbial inoculants can improve antioxidant capacity, cell-wall binding, vacuolar sequestration, nutrient homeostasis or rhizosphere immobilisation, yet much of this evidence derives from hydroponic, pot or short-duration experiments. A central limitation across the literature is the frequent use of physiological recovery as a surrogate for food safety. Treatments that improve biomass or oxidative-stress markers do not necessarily reduce metal concentrations in harvested organs, and some interventions can mobilise contaminants under changing pH or weathering conditions. The strongest practical approach is therefore an integrated, verification-based system in which interventions are selected according to contaminant source, soil chemistry, vegetable type and edible organ, and are judged primarily by marketable yield and contaminant concentrations in the harvested product. Long-term field trials, multi-metal experiments and genotype-by-environment validation remain priorities for translating mechanistic advances into reliable vegetable-production practice.