Using spatially explicit soil mapping and modelling to understand and mitigate nitrate leaching in an agricultural catchment

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Project summaryThis study uses digital soil mapping approaches, N models and agricultural management strategies to map and mitigate N losses to groundwater in a vulnerable catchment in north Northumberland. It will increase our understanding of the factors driving the spatial variability of soil-N dynamics at a scale that is relevant for producing farm and field-specific agronomic recommendations. The main objectives of this project are: a) To identify the source of Nitrate leaching and contamination of the Fell Sandstone aquifer through infield monitoring and soil N dynamic modelling, b) To identify and demonstrate the relation between nitrate leaching and agricultural practices in those specific areas, c) To evaluate the impact of mitigation strategies (natural nitrification inhibitors, slow release fertilizers, catch crops) on N leaching for different soil types without compromising crop production, and d) To produce a calibrated and validated N-dynamic model of nitrate leaching within soils relevant to the Berwick area. To achieve these objectives the project is divided into specific tasks including: review of current knowledge on factors controlling nitrate leaching and mitigation strategies in northern temperature cropping systems (literature review), monitoring and modelling of nitrate leaching, testing of proposed mitigation strategies, and predicting spatial variability of N leaching under different management strategies in the Fell Sandstone catchment. The factors driving spatial variability of N leaching in the catchment will be studied using porous cup methods for N leaching measurement, detailed information on past crop management, conductivity and Gamma-Radiometer soil sensors to map soil properties, and Digital Elevation Models (DEM), all integrated using the latest Digital Soil Mapping (DSM) techniques. Selected mitigation strategies will be implemented in high risk fields and data regarding nitrate leaching and crop growth will be collected throughout the year. Ideally, landowners will be encouraged to use a strip approach to implementing the measures so that some comparisons with standard practice are possible. The soil N dynamic model (NDICEA) will be calibrated and validated using observed data of soil properties and nitrate leaching. The calibrated model will be used to predict impact of different agricultural management practices on nitrate leaching to ground water from agricultural catchments. At the end of this research we expect to be able to identify variable soil types and key soil properties that can support nitrate leaching from an agriculture catchment. We will identify appropriately effective catchment management techniques to mitigate nitrate leaching and the result will be a proof for farmers that these strategies work to reduce nitrate leaching without compromising productivity. We will have validated model and approach to predict nitrate leaching based on measurable properties that can be used to identify risk of nitrate leaching from different soil types under different management practices.