Immobilization of cadmium in soil and improved iron concentration and grain yields of maize (Zea mays L.) by chelated iron amendments

With the development of industrial and agricultural production, the cadmium (Cd) pollution in farmland soil is increasing which threatens the quality and safety of agricultural products in China. The purpose of this research is to explore the potential of chelated iron amendments for reducing the bioavailability of Cd to maize plants. The experiment of maize cultivation was carried out in pots. Maize was cultivated in brown soil collected from a northeast region in China and then artificially contaminated with Cd with an average concentration of 10 mg/kg. The potential of ethylenediamine tetra acetic acid ferric-sodium (EDTANa(2)Fe) and ethylenediamine-N, N'-bis(2-hydroxyphenylacetic acid) ferric-sodium (EDDHAFe) as amendments for Cd immobilization in soils were tested. Effects of different concentrations (0.013, 0.026, 0.053, and 0.08 g/kg) of EDTANa(2)Fe and EDDHAFe (calculated by iron) on the growth of maize and the Cd and Fe uptake in maize were evaluated. Principle component analysis (PCA) was performed to further analyze the overall effects of iron amendments on Cd accumulation in plants. The results showed that EDTANa(2)Fe and EDDHAFe at dose of 53 mg/kg reduced available Cd in soil to the value of 5.19 and 4.59 mg/kg, respectively. EDTANa(2)Fe of 80 mg/kg and EDDHAFe of 26, 53, and 80 mg/kg increased Fe concentration in grains by 34.86%, 36.88%, 41.46%, and 44.05%, respectively, while reduced the Cd content in grains by 39.82%, 42.67%, 48.41%, and 35.08%, respectively. Fe concentration in grains showed a significant negative correlation with the concentration of Cd (P < 0.05). EDTANa(2)Fe of 53 mg/kg treatment increased the maize yield by 30.45% which was higher than in all other treatments. EDDHAFe treatments of 26 and 53 mg/kg increased the total root length by 39.72% and 48.68%, respectively, and increased the total root surface area by 19.95% and 22.98%, respectively. In general, the application of EDTANa(2)Fe and EDDHAFe at dose of 53 mg/kg can effectively immobilize Cd in soil and reduce Cd accumulation in maize and improve Fe uptake in grains.