Biochar Mitigates Arsenic Phytotoxicity and Improves Crop Performance in Iron‐Rich Tropical Soils

ABSTRACT The contamination of tropical soils by the highly toxic metalloid, arsenic (As), is a pervasive issue, resulting in declining crop performance due to phytotoxicity. Biochars are gaining popularity as sorbents for contaminants, yet their capacity to ameliorate As phytotoxicity in diverse tropical soil types remains underexplored. This study investigated the interactive effects of biochar and As on the growth and physiology of rice ( Oryza sativa ) and potato ( Solanum tuberosum ) across two distinct tropical Oxisols: agricultural soil and iron‐rich soil. While the experimental design focused on biochar × arsenic interactions without a standalone biochar control, results indicated that biochar effectiveness is highly soil‐mineralogy dependent. In the Fe‐rich soil, biochar significantly mitigated As‐induced stress, as evidenced by a 44% increase in potato biomass. Furthermore, biochar application in arsenic‐contaminated iron soils significantly improved the maximum quantum yield of Photosystem II ( F v / F m ) by 39% over arsenic‐only treatments ( p < 0.001), restoring absolute F v / F m values from a severely stressed state (~0.55) to a more physiologically stable range (~0.76). In contrast, biochar application in the agricultural soil was less effective and, in some cases, exacerbated growth inhibition. These findings suggest that while biochar is a promising tool for mitigating As‐induced phytotoxicity in Fe‐rich tropical environments, its application must be soil‐specific. Future research should quantify tissue As concentrations to confirm dietary risk reduction.