Effects of Nitrogen, Phosphorus and Potassium Fertilizers on Heavy Metal Uptake and Accumulation by Maize Seedlings

Lead(Pb), cadmium(Cd) and arsenic(As) are heavy metals with wide research attention. A pot-trial test was carried out under Pb-Cd-As compounded pollution conditions to study the effects of nitrogen(NH4Cl), phosphorus(Na2HPO4) and potassium(KCl) fertilizers on seedling growth, heavy metal uptake and accumulation of maize(Zea mays), which is a high-biomass plant. The results indicated that a significant change was observed in biomass(shoot and root) and heavy metal uptake of maize under different fertilizations and fertilizer concentrations. NH4Cl could significantly increase the aboveground biomass of maize and the accumulated Pb and Cd concentrations in plants. The extractability of Pb, Cd and As increased 1.7, 2.0 folds and 1.2 folds, respectively, with the application of NH4Cl. Both fertilizations and their concentrations could significantly affect the accumulation of Pb in plant. However, Na2HPO4 significantly reduced Pb bioavailability in soil at medium concentration(200 mg·kg-1), but significantly increased bioavailable As concentration in soil, which in turn significantly increased As accumulation in the shoots of maize at high Na2HPO4 concentration(400 mg·kg-1). Under different levels of fertilizer concentrations, Pb extraction by potassium was significantly higher than that by nitrogen and phosphorus. Compared with the control, KCl could increase Pb extraction for 2.4 folds in aboveground tissues of maize at low concentration(100 mg·kg-1). NH4Cl was the most effective fertilizer in enhancing phytoremediation of Pb-Cd-As contaminated soil by maize.