Abschätzung des Risikos einer Schwermetall-Akkumulation in Böden durch längerfristige Anwendung von Recycling- Phosphor-Düngemitteln

Summary

In order to assess the risk of the use of recycled phosphorus (P) fertilisers for organic farming, the potential accumulation of heavy metals in soil after a 200-year fertilizer application equivalent to 11 kg P ha-1 yr-1 was calculated in a mass balance approach. Both fertilizers currently allowed in organic farming and recycled P fertilizers were regarded. For heavy metals, four scenarios with two soil pH levels (pH 5 and pH 7) and two precipitation excess levels (F 0.1 and F 0.3 m yr-1) were calculated. Recycled P fertilizers like struvite, meat- and bone meal, ashes, sewage sludge and digestate, as well as phosphate rock and triple superphosphate had a higher P content and a lower heavy metal-to-P ratio than composts. Consequently, compost application was associated with the highest pollution risk. Only the Cd accumulation with TSP was higher than that with compost. Model calculations do not indicate a significant risk of heavy metal accumulation in soil compromising food quality or soil fertility after longterm application for the assessed recycled P fertilizers.