The main objective of this work was to develop regional settings of the NANI budgeting tool that will address the significant variation in agricultural practices and resulting nutrient accountings among European countries.
NANI (Net Anthropogenic Nitrogen Inputs), first introduced by Howarth et al. (1996), estimate the human-induced nitrogen inputs to a watershed and have been shown to be a good predictor of riverine nitrogen export at a large scale, multi-year average basis. NANI have been calculated as the sum of four major components (Figure 1.A): atmospheric N deposition, fertilizer N application, agricultural N fixation, and net food and feed imports, which in turn are composed of crop and animal N production (negative fluxes removing N from watersheds) and animal and human N consumption (positive fluxes adding N to watersheds). Assuming approximate steady-state behavior, riverine N export is a fixed proportion of net nitrogen inputs.
Similar calculations can be made for phosphorus (P) inputs, though because atmospheric deposition of P is usually considered negligible and there is no analog in P for atmospheric fixation, the calculation of Net Anthropogenic Phosphorus Inputs (NAPI) reduces to accounting for P fertilizer and P in net food/feed terms. While this document is primarily concerned with calculating NANI, we also describe the data sources and assumptions used to make the parallel calculations of NAPI.
Version 2.0 of the Toolbox described in this document is an improvement of version 1.0 developed for US watersheds (Hong et al. 2011). Version 1.0 allows the user to calculate NANI in any area within the contiguous United States (e.g., watershed, county, etc.) from nationally available databases downloadable from the Internet.
The toolbox consists of a set of tools that:
(1) calculate the proportions of various regions (political or gridded) in which data are collected that fall into areas of interest such as watersheds (“NANI-GIS tools”),
(2) extract and organize relevant data downloaded from web-based datasets to be used by the accounting tools (“NANI-extraction tools”), and
(3) calculate NANI, their components, and other relevant items such as animal excretion (“NANI-accounting tools”).
Version 2.0 NANI/NAPI Calculator Toolbox
Version 2.0 of the Toolbox described in this document has several modules and improvements added to version 1.0 (which assumes spatially uniform agricultural practices, i.e., fixed values for all the NANI parameters, supported by the availability of well-established and standardized datasets) to address the above difficulties. These improvements include:
• Allowing spatial variation of NANI parameters (in this example, country-specific NANI parameters) (Sections 4, 5.1, and 5.2)
• Distribution of regional data (e.g., country-level crop production) into smaller spatial units (e.g., grid cells containing crop area information) (Section 5.3)
• Making post-calculation adjustments and refinements by accepting auxiliary datasets and manual calculations from the user (Section 3)