Revealing effective strategies for cadmium reduction in rice: A meta-analysis of modified biochar applications

Cadmium (Cd) contamination in paddy soils poses substantial environmental and health risks, particularly in regions where rice is a dietary staple. Modified biochar (MBC) has been identified as a promising approach for mitigating Cd accumulation in rice; however, the comparative effectiveness of different modifications relative to unmodified biochar (UMBC) remains insufficiently quantified. This meta-analysis integrates data from 1164 paired observations across 51 studies to assess the influence of MBC on Cd accumulation in brown rice. The findings indicate that MBC reduces Cd accumulation by 27.6 %, primarily by limiting root uptake and restricting translocation to grains . Notably, biochar modified with calcium, iron-manganese, iron-calcium, bacterial inoculants, and minerals exhibited significant Cd reduction, whereas silicon and alkaline modifications had minimal effects. The most effective Cd reduction was observed with 1–3 % biochar application at pH 7–9 under flooded conditions, with the medium-season rice crop showing the most pronounced response. These findings provide critical insights into the selection of effective biochar modifications and the development of practical, cost-efficient remediation strategies for Cd-contaminated rice paddies . • Modified biochar reduced Cd levels in brown rice by 27.6 % compared to unmodified biochar. • Lower Cd uptake and limited translocation led to reduced Cd in brown rice. • Ca, Fe-Mn, Fe-Ca, bacterial, mineral, and Fe biochars were more effective in reducing Cd than Si/alkaline biochars. • Optimal Cd reduction occurred with 1–3 % biochar at pH 7–9. • Flooded conditions and the middle rice season showed the most significant Cd reduction.