Global Nitrogen Innovation Center for Clean Energy and the Environment

Objectives
Use of nitrate and urea inhibitors represent one of the nitrogen management practices which can contribute to the mitigation of potential GHG emissions associated with the deployment of fertilisers in agricultural settings. Active research is being undertaken to improve our knowledge about the efficacy of their application in a controlled experimental setting. To examine the potential efficacy at regional scale for strategic planning, there is a need for the better understanding about the spatial patterns of various factors which affect their potential impacts at management scale.

Selection of controlling factors:
Based on existing literature reviews (e.g., Fan et al., 2022), significant environmental and management factors were selected, comprising:

• Soil pH
• Soil texture / soil drainage
• SOC content
• Average air temperature after applications: Mar to May for arable and Apr to Sep for grass
• Cumulative rainfall after applications: Mar to May for arable and Apr to Sep for grass
• Soil moisture
• Fertiliser application rate and total load

Identify mappable data sources:
Recent accessible data with national coverage and reasonable spatial resolutions were sourced and processed. Most soil properties, i.e., pH, soil texture and SOC content, are based on NatMap1000 (c.f. LandIS) where dominant soil series at 1 km grid have been identified and their associated attributes sourced. For soil drainage status, existing pedotransfer functions were employed to group different soil series into free draining and other (i.e., assisted) drainage types (Zhang et al., 2017). For climate variables, e.g. such as air temperature and monthly rainfall, HADUK-Grid data (Met Office, 2018) on long term monthly averages for years between 1991 to 2020 was used. To characterise the dynamic of soil water contents in surface soils, mapped soil moisture patterns merged from satellite and modelled data (Tanguy, 2022) were further processed to derive the information presented here. To quantify nitrogen fertiliser applications for different groups of crops, reported rates from annual surveys of fertiliser practice for various land uses and crops between 2020 and 2022 (Defra, 2024) were averaged to provide representative values.

Spatial data processing using ArcGIS:
The spatial distributions of selected robust farm types (Defra, 2014) were based on the recent June Agriculture Survey data in 2021. They were linked with mapped of environmental factors through geoprocessing in ArcGIS.

Summarised outputs for individual WMCs:
WFD Water Management Catchments (WMCs) for surface water were used as the base spatial units for data processing and presentation.

OpenStreetMap (OSM standard) was included as a base map to provide spatial context for users.