Alleviating cobalt and lead toxicity in rice using zero valent iron (Fe°) amendments

Simultaneous impact of zero valent iron (Fe°) and rice cultivar on uptake, translocation, and bioaccumulation of cobalt (Co) and lead (Pb) in rice (Oryza sativa L.) was investigated to alleviate Co and Pb toxicity in rice. Kilombero and Faya rice cultivars, amended with Fe° dosages of 0, 6.20, and 12.40 g Fe° kg−1 soil, were cultivated under continuous flooding in pots in a greenhouse. Shoot and grain-Co and Pb concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). For Co, amending Faya rice with at least 6.20 g Fe° kg−1 reduced grain-Co accumulation by 33% or more compared to control plants (F = 17.5; p < 0.001) while inconsistent results were obtained for Kilombero. For Pb, Faya also accumulated more than 39% less grain-Pb than control plants (272 μg kg−1) while Kilombero accumulated more than 55% less grain-Pb than control plants under the same conditions. Despite reducing grain-Pb accumulation in both cultivar, Fe amendments of at least 6.20 g Fe° kg−1 reduced grain-Pb accumulation with greater magnitude in Kilombero (55%) than in Faya (39%). Nonetheless, Fe amendments inhibited greater shoots-Co and Pb translocation (≥32%) to grains in Faya compared to Kilombero (≤20%). The work provides a novel promising agronomical practice of reducing Co and Pb bioaccumulation in rice. •Impact of rice cultivar x Fe° amendments on Co and Pb accumulation in rice grains was studied.•Fe° dosages markedly inhibited available Co and Pb in porewater.•Fe° dosages marked inhibited translocation of Co and Pb from shoots to grain.•Uptake of Co from soil was higher in Kilombero than in Faya while uptake of Pb was vice versa.•Co and Pb accumulation in rice grains varied with cultivar and Fe° dosages. Cobalt (Co); Faya, Kilombero, Lead (Pb); Rice; Zero valent iron (Fe°); Cultivar.