Nutrient release from Revaq sludge vs. mineral fertilizer – Implications for eutrophication effects from agriculture

Abstract: Many farmers today are using mineral fertilizers (MF) containing big amounts of nutrients like phosphorus and nitrogen, which can lead to e.g. eutrophication in watercourses. Due to this problem, the use of Revaq-certified sewage sludge (RS) as fertilizer has drawn some attention, both because it might be a better alternative than MF and for the return and circulation of phosphorus and nitrogen. The aim with this study was to see if there was any difference between these two fertilization methods when analyzing nutrients in leakage water from soil that had been fertilized with either: RS or MF. An experiment was carried out with soil in pots fertilized with either MF or RS. The soil was watered and the leakage water sampled and analyzed for total phosphorus and total nitrogen. The results showed a clear difference of nutrient concentrations between the MF and RS. Soil fertilized with MF released phosphorus in a higher concentration than soil with RS. The result for total nitrogen showed that MF also released higher nitrogen concentration than RS during the first days after. The conclusions is therefore that MF due to its high concentrations of released nutrients, might more likely contribute to eutrophication than RS.