Synoptic assessment of environmental impact of agricultural management: a case study on nitrogen fertiliser impact on groundwater quality,using a fine-scale geoinformation system

Regional assessment of agricultural impacts on the environment requires systematic integration of a range of data. To overcome various limitations, a synoptic approach would be useful for preliminary assessment of potential impact or for deriving hypothetical relationships at geospatial basis. The objective of this case study was to demonstrate the effect of a synoptic approach using a fine-scale geoinformation system in geospatial assessment of environmental impact, viz., the nationwide impact of nitrogen fertiliser on groundwater quality. All farmlands throughout Japan were expressed as polygons comprising a few hectares, and the system integrated a wide range of basic geospatial datasets including topographic data, soil type, meteorological data, drainage conditions, and detailed land-use conditions. The case study showed that nitrogen load from fertilisers was closely related to nitrate nitrogen (NO₃-N) of regional groundwater. A hypothetical regression model was derived from the synoptic data analysis. Results demonstrated the usefulness of comprehensive geospatial platforms for a wide range of agricultural and environmental applications.