At each site measurements were taken from sixteen plots, organised within a randomised complete block design. Four plots did not receive fertilizers (controls), four plots received urea only, four plots received urea and urea-inhibitors, and 4 plots received Ammonium-nitrate (Nitram). Cumulative NH3 emissions were measured using a wind tunnel technique, at a daily resolution for 21 days following each N fertiliser application. Nitrous oxide emissions were measured using a combination of static manual and static automatic (combined with an Isotopic N2O Analyser, Los Gatos Research Inc. San Jose, CA, USA) chambers. Using the manual static chambers, the resolution of N2O measurements following N fertiliser application was 3 x weekly for weeks 1 and 2, 2 x weekly for weeks 3 and 4, and 1 x weekly thereafter. Using the automatic static chambers, the resolution of N2O measurements following N fertiliser application was approximately every six hours. Samples for soil NH4 and NO3 analyses were collected at the same temporal resolution as the N2O sampling using manual static chambers. Herbage yield measurements were carried out on the day of cutting, and samples of the fresh-cut herbage were couriered within 24 h to external contractors (Trouw Nutrition GB, Blenheim House, Ashbourne, UK and Sciantec Analytical Laboratories, Stockbridge Technology Centre, York, UK) for quality analyses of (CP, ME, NDF, ADF and DM). Digestibility was calculated. All results were entered into Excel spreadsheets providing individual datasets for each set of N parameters. Data were exported from Excel as .csv files for ingestion into the EIDC.

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