TY - CONF A1 - Kratz, S. A1 - Samman, N. A1 - Wilharm, E. A1 - Jabs, K. A1 - Anlauf, R. A1 - Vogel, Christian A1 - Bloem, E. T1 - Development of a standard substrate to facilitate the use of DGT for the assessment of P recycling fertilizers N2 - P recycling fertilizers are gaining increasing importance in our efforts to close nutrient cycles. An unsatisfactory performance of standard chemical extraction methods to assess the fertilizing effects of such products was reported. They demonstrated that DGT extractions of incubated soil/fertilizer mixtures were able to predict the fertilizing effects of the respective products more accurately. Since DGT works with soil/fertilizer mixtures, its interpretation is soil-dependent. Therefore, in order to facilitate its use as a tool to predict fertilizer performance, it needs to be standardized based on a standard substrate. This research aims to develop a standard substrate based on which evaluation categories for the DGT fertilizer extraction can be derived. The substrate composition should allow to vary the most important soil properties determining the plant availability of fertilizer P. It must also be reproducible at any time and any place. Substrate variants with varying proportions of quartz sand, a clay mineral and sphagnum peat were prepared and set to pH-levels 5.5 and 7 by addition of CaCO3. 7 variants were incubated with a set of test fertilizers (2 recycling fertilizers based on sewage sludge ash and 2 conventional mineral fertilizers) for 2 weeks. Substrate/fertilizer mixtures were then extracted with DGT and an ANOVA was performed to test if the DGT extraction was able to depict significant differences between fertilizers and substrate variants. An 8-week pot trial with ryegrass (3 cuts) was set up with the same substrate variants and test fertilizers. P uptake was determined to assess the fertilizing effect and correlated with the results of the DGT extractions. Statistically significant differences were found between DGT results for the various test fertilizers and substrate variants, indicating that DGT is able to differentiate between P solubility of fertilizers in relation to substrate quality. DGT results showed a strong relationship with P uptake, confirming that this method is suitable to predict the fertilizing effect of P fertilizers. Further optimization of substrate composition and tests with a wider variety of crops and fertilizer types are needed, before evaluation categories for DGT values can be derived. T2 - 6th Conference on Diffusive Gradients in Thin Films CY - Vienna, Austria DA - 17.09.2019 KW - Fertilzer KW - Phosphorus KW - Diffusive Gradients in thin films (DGT) PY - 2019 AN - OPUS4-49060 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -