Deinking paper fibre application to agricultural land: soil quality enhancer or copper polluter?

Short‐fibre paper residuals (deinking paper fibre (DPF) or paper mill sludge) represents a major waste formed during the processing of recycled paper and is known to contain significant quantities of copper. It is often spread onto agricultural land to help increase soil pH and improve structure by adding soil organic matter (SOM). A number of agricultural sites in England and Wales that had received large and repeated applications were sampled to investigate the long‐term effects of this practice on soil quality and plant copper content. We found that the composition of DPF waste has changed significantly between 1999 and 2006 with concentrations of Cu increasing and organic matter content declining. Whilst repeated additions of DPF to agricultural land always increased soil Cu, an associated increase in SOM was not always apparent. There was no link between SOM and bioavailable Cu nor between soil bioavailable Cu and plant Cu. In contrast to previous reports, our findings indicate that improvement in soil quality following the long‐term application of DPF was site‐specific and in some cases it may have reduced soil quality rather than enhanced it.