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To get more detailed information on nutrient budgets in organic apple orchards, a case study was conducted in the Alte Land region (Lower Saxony, Germany). Semi-structured inter-views with organic apple growers and soil analyses of selected orchard sites were performed in order to verify how the fertilization practices affect the level of soil nutrients. The test of several alternative sources of organic fertilizers was carried out in field trials on organic apple located in Switzerland (FIBL), Italy (LAIM), Bulgaria (FGI), Poland (IN-HORT) and Germany (UHOH). As production intensities differed between the locations, different target N levels were applied by the project partners. In addition, since the sources of alternative fertilizers differ depending on the European region, the choice of the fertilizers was based on the product availability for local farmers. In Germany, for instance, access to com-mercially produced biogas digestates and composts is easy for organic growers, but this is not the case in Bulgaria. However, a common standard fertilizer, horn grit, was used on all sites in addition to an unfertilized control to allow for a multi-site comparison. At FGI, INHORT and UHOH field trials in intensive apple orchards were done for two (FGI) or three years (INHORT, UHOH), testing the fertilizers under conditions of local cultivation practices. Moreover, in order to better understand the N dynamics, incubation (LAIM) and pot trials (FIBL, LAIM) were carried out.

The report provides guidelines for the development and implementation of fertilization strategies using alternative fertilizers in intensive organic apple orchards based on the findings of the DOMINO project. It shall be noted that further scientific journal contributions will be published to provide a more detailed insight of the findings of our project. The current guidelines aim to provide strategies for a site-specific adoption of fertilization strategies for alternative fertilizers.