Impacts of Long-term Livestock Manure Application on Heavy Metal Accumulation in a Typical Fluvo-aquil Soil
An experiment was conducted since 2001 to study the accumulation, fraction change and transfer of heavy metals in soils under long-term livestock manure application. The treatments of field experiment included OM (pig manure) and balance-fertilization of chemical fertilizers (NPK). The results showed that over 13 years (2001—2013) of livestock manure application, Cu and Zn in soils, especially in tillage layer (0–20 cm) significantly accumulated, But in 2013 heavy metal concentrations (Cu: 38.71 mg/kg; Zn: 83.26 mg/kg) were very low, loading little negative effects on eco-agricultural safety. Results of sequential extraction showed that Cu, Zn, As concentrations in DTPA-, acid soluble (EXCH-), reducible (FeMnOX-) and oxidizable (OX-) factions under OM treatment were significantly higher than those in NPK treatment. However, Cr, Pb and Cd stabilized in soils, was less affected by different fertilizations. The dominant fraction of Cr in soil was residual fraction (RESD-) (>95%). Most of Cu added by livestock manure was accumulated in RESD- fraction (>50%), while added Zn was easily accumulated in EXCH- (40%) fraction and in FeMnOX- (60%) fraction. Long-term application of livestock manure is not only the major source of soil heavy metals, but also significantly affect their fractions through changing soil properties, which are also important reasons for more metals transferred to deeper soils.
Heavy metalLivestock manureAccumulationFraction changeTransfer
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