Foliar control agents for reduction of Cd accumulation in rice grains: A meta-analysis

Heavy metal contamination in rice threatens human health. Foliar control agents could effectively reduce cadmium accumulation, but their effectiveness, cost, and underlying mechanisms vary. Therefore, this study comprehensively compared the differences of cadmium reduction, mechanism, yield, and cost with meta-analysis to evaluate and recommend effective foliar control agents. The results showed foliar control agents can be categorized into inorganic and organic types, where the inorganic types include non-metallic and metallic, while the organic types include organic acid, natural active substances, and others. In a field experiment, organic control agents showed better performance than inorganic control agents, the reduction of cadmium accumulation in grains showed 0.18 mg/kg and 0.12 mg/kg, respectively. The organic foliar control agents increased the fixation of cadmium in cell walls, while for inorganic foliar control agents, the accumulation of cadmium both in cell walls and organelles was increased. For field application, the organic foliar control agents were increase 419.35 kg/ha of yield, while the effectiveness of inorganic agents was weaker, only increasing 225.82 kg/ha. In terms of cost (reagent and labor cost), organic foliar control agents (361.42-1867.00 CNY/ha) were higher than inorganic foliar control agents (510.19-10633.33 CNY/ha). Considering the cost, yield, and reduction of cadmium, Serine, NaH 2 PO 4, and Na 2 SeO 3 were recommended when soil cadmium content ranged from 0.4 mg/kg to 0.8 mg/kg. Na 2 SiO 3 and Tetraethyl silicate were recommended when cadmium levels in agricultural soils exceed 0.8 mg/kg. Through mechanistic elucidation of foliar control agents and cost-yield optimization analysis, this work provides a scientific foundation for developing advanced foliar immobilization technologies. • A meta-analysis was conducted to assess the effects of foliar control agents on cadmium reduction, yield, cost, and underlying mechanisms. • Inorganic agents outperformed organic ones in reducing Cd accumulation in pot experiments, but the trend reversed in field trials. • Organic agents increased yield by 193.55 kg/ha compared to inorganic agents. • The cost of organic agents (510.19-10633.33 CNY/ha) was significantly higher than inorganic agents (361.42-1867.00). • Organic agents enhanced Cd fixation in cell walls, whereas inorganic agents increased Cd accumulation in both cell walls and organelles.