The aim of the project Biobased Fertilisers Achterhoek (‘Kunstmestvrije Achterhoek’ in Dutch) is to make fertilisation practices more sustainable through 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 is to determine the nitrogen fertiliser replacement value of biobased fertilising products made from animal manure. A second objective is 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 with field experiments on grassland and on arable land with silage maize. This document reports the results of a field experiment on grassland which was conducted in 2020. The field experiment on grassland points on a similar agronomic effectivity of the biobased nitrogen fertilising product compared to calcium ammonium nitrate. The environmental performances of all fertilising products with equal rates of nitrogen were comparable.