# denit\_frac

This parameter defines the fraction of field capacity water content above which denitrification takes place. Denitrification is the bacterial reduction of nitrate (NO3) to N2 or N2O gases under anaerobic (reduced) conditions. Because SWAT+ does not track the redox status of the soil layers, the presence of anaerobic conditions in a soil layer is defined by this variable. If the soil water content calculated as a fraction of field capacity is ≥ *denit\_frac*, then anaerobic conditions are assumed to be present and denitrification is modeled. If the soil water content calculated as a fraction of field capacity is < *denit\_frac*, then aerobic conditions are assumed to be present and denitrification is not modeled.


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://swatplus.gitbook.io/io-docs/introduction-1/basin-1/parameters.bsn/denit_frac.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.