All crops need phosphorus (P) to grow. Negative P budgets deplete the soil’s P reserves in the long term. In organic farming, there are only a few permitted P sources. Use of P fertiliser can be crucial, especially when reliance on biological nitrogen (N) fixation is high. Solution Struvite (magnesium ammonium phosphate) is a naturally occurring mineral used to satisfy plants’ phosphorus needs. Struvite obtained from municipal wastewater treatment plants allows P recycling (including some N) and can thus partially replace non-renewable P sources. Outcome Depending on the process, normally 12-22% of P present in wastewater is recovered in struvite. The P in struvite is not water-soluble but soluble in weak organic acids, such as those present in root exudates. The quality and purity of the final product depends on the production process, but contaminant levels are generally very low.

Else Bünemann, Research Institute of Organic Agriculture (FiBL), IFOAM Organics Europe