The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) is to make fertilisation practices more sustainable through the use of locally available nutrients from renewable sources. The project is part of the Sixth Action Programme of the Netherlands which serves the Nitrates Directive. One of the objectives was to determine the nitrogen fertiliser replacement value of biobased fertilising products made from animal manure. A second objective was to assess the risk of nitrogen leaching from these biobased fertilising products. These objectives were implemented by WUR-Wageningen Environmental Research in a monitoring programme that included field experiments on grassland and on arable land with silage maize. This document reports the results of a field experiment with silage maize which was conducted in 2020.