© 2015, Springer-Verlag Berlin Heidelberg. Purpose: Using river sediments as a soil amendment has hundreds to a thousand years of history in the river plain network region of southern China. This study aimed to investigate the pollution conditions of heavy metals in cultivated soils consistently amended with river sediments for a long term. Materials and methods: Soil samples were collected in agricultural fields which were amended with river sediments for a long term. Soil heavy metals (Cr, Ni, Cu, Zn, Pb, Hg, As, and Cd) were determined and then assessed using Nemerow’s comprehensive pollution (NCP) and potential ecological risk (PER) indices. A combination of correlation, principal components, and hierarchical cluster analysis was employed to analyze the source of soil heavy metals. Results and discussion: Soil Cu, Zn, Ni, Cd, and Cr exceeded the Chinese criterion with excessive Ni levels (719.0 %) in paddy soils and Cu levels (367.8 %) in dryland soils. Soil Cd and Hg had moderate levels of ecological risk. The contamination of soils with heavy metals was graded as heavy by the NCP index or high (paddy soils) and moderate (dryland soils) by the PER index. That is, the soils have accumulated serious levels of heavy metals according to the Chinese assessment criterion. The source of heavy metals in the studied soils is shown to be mainly attributed to anthropogenic activities and environmental effects (e.g., river sediment application, atmospheric deposition). Conclusions: Therefore, as a traditional practice for soil amendment, the use of localized river sediments in this region should cease until the quality of the sediments has been assessed.