Calcium-pH interplay modulates cadmium accumulation in Arachis hypogaea: Implications for safe peanut production

Balancing soil pH and Ca supply boosted peanut yield by 41.2% in the acidic soil. Slight pH increase had limited effect on reducing Cd accumulation in peanut seeds. Ca enhanced both root Cd absorption and Cd immobilization in shoot cell walls. Balanced soil pH and Ca increased peanut yield and reduced seed Cd content. Adjusting soil pH and supplementing calcium (Ca) are widely adopted agronomic practices for peanut cultivation in acidic soils, but their role in modulating cadmium (Cd) accumulation remains poorly clarified. Therefore, pot and hydroponic experiments were both conducted to assess the impacts of lime application (at a rate of 0.7%) and Ca application in the form of Ca(NO 3 ) 2 at varying levels (0.01, 0.02, and 0.04%) on Cd bioavailability in an acidic soil and its uptake by peanut. Results demonstrated that lime and Ca(NO 3 ) 2 individually reduced seed Cd concentrations by 15.7 and 30.4%, respectively, while their combined application increased peanut yield and reduced Cd concentration in seeds. Lime predominantly reduced Cd accumulation by limiting its uptake through root; while Ca(NO 3 ) 2 increased Cd in the soil solution but promoted Cd sequestration in shoot cell wall, ultimately restricting Cd translocation to pods. Additionally, hydroponic experiments under acidic to near-neutral conditions revealed a parabolic response of Cd uptake to the changes in pH and Ca concentration. The maximum Cd uptake was noticed at pH 6.0 with 1 mmol L -1 Ca application (Ca/Cd=2,000). The notable decrease of Cd uptake were observed at higher pH 7.5 and Ca>1 mmol L -1 , but it also cause the reduction of plant biomass. These findings demonstrate that the optimization of pH and Ca 2+ levels is necessary to enhance peanut yield and minimize Cd translocation to edible seeds.