description_osi_nitrogen.Rmd

---
title: "Description of osi_nitrogen"
author: 'Elise van Eynde & Gerard Ros'
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Description_osi_nitrogen}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

This document explains how the phosphorus indicator is calculated for each country and provides references


## Netherlands:



## Belgium (Flanders): 

## France:

Principle:

Cropland:
20 digital support systems for N are available in France. Our method is based on AzoFert (doi:10.3390/agronomy7040073). 
Mineralisation of nitrogen is calculated per 10 days, taken into account (1) organic nitrogen (2) clay and CaCO3 content (3) ratio inert:active N fractions (33% for all soils since no sufficient data is available) (4) Fsyst based on management or organic residues, we treat all soils the same so put at 1 (5) f(t) temperature factor based on mean temperature and (5) moisture correction based on field capacity and wilting point 

Since we are only interested in soil properties, we take only into account the potential mineralisation of N without temperature and moisture correction 

Mh = 22/((12+clay%)x(545+limestone%))*Norg*0.33 *fT * gW, multiplied with 21.35 to get it into years since this formula is calibrated for 10 days. We used 7 months as maximal growing period (7 x 30.5 = 213.5) with 33 % considered as reactive from the total Norg

fT: correction for temperature: e^(K*(Tmoy-Tref)) with K 0.115, Tmoy mean temperature and Tref reference temperature (15 degree).
COPERNICUS CAN BE USED FOR TEMPERATURE, BUT WHICH PERIOD SHOULD BE CONSIDERED?

gW: correction for moisture: 0.2+0.8((Wsl-Wwp)/(Wfc-Wwp)) with Wsl soil moisture content, wilting point and field capacity. 
Wilting point and field capacity can be calculated using soil textural classes with eutptf package: https://rdrr.io/github/melwey/euptf/man/euptf-package.html; soil moisture content can be derived from COPERNICUS BUT WHICH PERIOD SHOULD BE CONSIDERED. 

We used the same limit values as for the NL to get the score (arable vs grassland)



Bulk density was calculated by using the empirically derived function for European cultivated topsoils  doi: 10.1111/j.1365-2389.2011.01412.x
This calculation was now directly included in the function of N, not separately as done for the OBIC

Grassland: