NuGIS Data Transformation Workflow Model.

The Nutrient Use Geographic Information System (NuGIS) project (http://www.ipni.net/nugis) directed by the International Plant Nutrition Institute uses a variety of data sources for determining mass balance nutrient budgets at the county and 12-digit hydrologic unit code scale (HUC12). Two challenges to the NuGIS project include 1. sparse or missing data at the county level for fertilizer use, cropping systems, and livestock production and 2. spatial transformation of county data to subwatersheds. NuGIS has developed methods for healing missing data and using spatial models to migrate data from county level to subwatersheds. This paper steps through the datasets used in NuGIS explaining their use, their limitations, and steps used to migrate data from the initial spatial resolution to the county scale and then to HUC8 and HUC 12 watershed polygons on a national scale. This process is explained via maps and equations in a raw to processed data workflow diagram. Data validation checks are highlighted and explained. This paper provides transparency to the NuGIS process and identifies data availability and reliability issues regarding crop nutrient calculations.