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Summary

Organic farming systems with restricted access to animal manure often experience decline in soil P concentrations. Nutrients should be cycled in society to maintain the long-term fertility of agricultural soil. One option for this may be precipitation of struvite (magnesium-ammonium phosphate) from sewage treatment plants, to be Applied as fertiliser. Struvite produced in a Norwegian sewage plant (Hias IKS)significantly increased yield levels and soil P concentrations, when applied in one season (2018) in a long-term experiment comparing two levels of manure application at Tingvoll research farm, NW Norway. Struvite has been proposed by the Expert Group EGTOP to be included in Annex 1, listing permitted fertiliser inputs in organic farming. However, a general allowance for struvite on the European level is by November 2019 still pending, hence hampering also an EU-allowance in organic farming. Several countries, e.g. Norway, allow for use of struvite in agriculture in general.