> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-3-nutrients-pesticides/chapter-3-1-nitrogen/3-1.5-atmospheric-deposition/3-1.5.2-nitrogen-dry-deposition.md).

# 3:1.5.2 Nitrogen Dry Deposition

Dry deposition of nitrate and ammonia is input to the model for each subbasin. Average daily deposition is added to the appropriate surface soil pool.

$$NO\_{3\_{ly=1}}=NO\_{3\_{ly=1}}+NO\_{3\_{drydep}}$$                                                                                                                       3:1.5.3

$$NH\_{4\_{ly=1}}=NH\_{4\_{ly=1}}+NH\_{4\_{drydep}}$$                                                                                                                      3:1.5.4

where $$NO\_{3\_{ly=1}}$$ is the $$NO\_3$$ in the surface soil layer, $$NH\_{4\_{ly=1}}$$ is the ammonium in the surface soil layer, $$NO\_{3\_{drydep}}$$ is the daily nitrate dry deposition rate (kg/ha) and $$NH\_{4\_{drydep}}$$ is the daily ammonium dry deposition rate (kg/ha).

Table 3:1-5: SWAT+ input variables that pertain to dry deposition.

| Definition                                | Source Name | Input Name | Input File |
| ----------------------------------------- | ----------- | ---------- | ---------- |
| Daily nitrate dry deposition rate (kg/ha) | drydep\_no3 |            | .atm       |
| Daily ammonia dry deposition rate (kg/ha) | drydep\_nh4 |            | .atm       |