Spatial patterns of essential trace element concentrations in Swedish soils and crops

Trace element (TE) concentrations in topsoil of Swedish arable soils and grain of winter wheat, spring barley and oats are regularly monitored. Data on Co, Cr, Cu, Mn, Mo, Ni and Zn were analysed in this study, in order to determine spatial patterns of geographical variation in concentrations and their correlations with soil parent material and bedrock geology, and to identify areas with possible TE deficiency or excess with regard to crop and livestock production and product quality. The results showed that pseudo-total (7 M HNO3 extraction) concentrations of Co, Cr, Cu, Ni and Zn were elevated in heavy clay soils. Areas influenced by sedimentary rock containing alum shale clearly showed elevated concentrations of various TEs, but otherwise it was difficult to find a clear correlation between soil TE concentration and bedrock geology. This may be because in the recently glaciated Swedish landscape, the ice sheet itself and the melt water from the declining ice sheet have transported soil material over large distances and/or because of low sampling density in many parts of the country. Despite weak correlations for individual elements, there was a general correlation between concentration in soil and concentration in cereal grain for many of the elements studied. One exception was Mn, for which pH was much more important than the concentration in soil. However, there was large variation in TE concentrations within short distances, indicating that soils with high and low concentrations can exist side by side. Nevertheless, for most TE, the risk of low concentrations in crop plants appeared to be greatest on coarse-textured soils on felsic rock and on soils on sedimentary rock (other than alum shale) in southern Sweden. While soils in this region generally have lower concentrations of Co, Cr, Cu, Mn, Ni and Zn than soils in most of western and central Europe, it was difficult to find documented deficiency of elements other than Cu and Mn among those that are essential to plants. Comparing the data on cereal grain presented on this study with suggested critical values indicates possible Cu and Ni deficiency. For the cationic TEs, the generally lower pH in arable soils in Sweden may be one explanation for the modest deficiency problems observed despite rather low soil concentrations. No excessive TE concentrations in crops were recorded, but on clayey soils in eastern Sweden the concentrations were higher than the national average. © 2017 Elsevier B.V.

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DOI:

https://doi.org/10.1016/j.geodrs.2017.07.001

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