Effects of mixed pulp mill sludges on crop yields and quality

There is a great need for sustainable fertilisers and soil amendments, as current fertilisation practices negatively affect the environment. Pulp mill sludges (PMS) could provide a means to replace fertilisers made using non-renewable resources while adding slowly decomposing organic material to the soil and utilising nutrients from the forest industry. This study tested the effects of composted and lime-stabilised mixed PMS (CPMS and LPMS) on wheat (Triticum aestivum) yields and residual effect on oat (Avena sativa) yields in the boreal region. A two-year field experiment included two CPMS and two LPMS treatments all with additional mineral fertilisation, a mineral fertiliser treatment, and a zero-control treatment. All the fertilisers increased yields. There were no differences in crop yields between CPMS, LPMS and mineral fertiliser treatments. However, some quality characteristics and nitrogen (N) uptake were lower with all or some PMS compared with mineral fertilisation. This result suggests that part of the mineral fertilisation for cereals could be replaced by using PMS, but more information on N mineralisation from sludges is needed.