Fertilizer Application Affects the Migration and Transformation of Cd and Pb in Agricultural Soils

Abstract

Long-term application of fertilizer has a significant impact on altering soil chemistry and physics. A better understanding of the relationship between fertilizer application and heavy metal(loids) migration in soil is necessary to minimize the health risks. The leachability and chemical forms of soil cadmium (Cd) and lead (Pb) under ammonium dihydrogen phosphate fertilizer (MP) and livestock manure (OM) applications were studied in four agricultural soils. The leaching experiment revealed that the leachability of Cd and Pb was increased by MP and OM applications. The Cd leaching rate increased from 0.01% to 0.22%―1.4% with MP treatment and 0.05%―0.15% with OM treatment. Similarly, the Pb leaching rate increased from 0.0001% to 0.0004%―0.31% (MP treatment) and 0.003%―0.03% (OM treatment), respectively. Redundancy analysis (RDA) indicated that Cd leachability was negatively correlated to soil solution pH; while Pb was strongly correlated to dissolved organic carbon (DOC). Soil incubation further demonstrated that the application of MP and OM led to a redistribution of Cd and Pb forms. Specifically, Cd and Pb transformed from residue and Fe/Mn oxide forms to organic or exchangeable forms. This study offers a new insight into the effects of fertilizer applications on the migration and transformation of heavy metal in agricultural soils.

Keywords: Leaching behavior, Soil incubation, Chemical forms, Fertilizer application