The data consists of nitrogen (N) offtake, N emissions and soil N parameters, and herbage quality parameters from a three-cut silage plot trial located at two grassland sites within the UK collected between April and October 2016. The sites were Rothamsted Research at North Wyke in Devon and Bangor University at Henfaes Research Station in North Wales. At each site measurements were taken from 16 plots, organised within a randomised complete block design. Fertiliser was applied three times and three cuts were performed, all parameters measured were following a fertiliser application. Nitrogen parameters measured were crude protein (CP) of herbage, ammonia (NH3) emissions, nitrous oxide (N2O) emissions, and soil ammonium (NH4) and nitrate (NO3). Herbage quality parameters measured were dry matter, acid-digestible fibre (ADF), ash, CP, metabolizable energy (ME), and non-digestible fibre (NDF) and digestibility (D) was calculated. Nitrogen offtake, losses and fluxes were measured to determine the N use efficiency and the economic viability of different N fertilisers. Measurements were undertaken by members of staff from Bangor University, School of Environment, Natural Resources & Geography and Rothamsted Research, Sustainable Agricultural Sciences – North Wyke. Data was collected for the Newton Fund project "UK-China Virtual Joint Centre for Improved Nitrogen Agronomy". Funded by Biotechnology and Biological Sciences Research Council (BBSRC) and NERC - Ref BB/N013468/1 Full details about this dataset can be found at https://doi.org/10.5285/4c7d4b3c-88f7-43ab-a50f-b6804474e568