> 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/introduction-1/soils.md).

# Soils

The physical soil properties are summarized in the file [**soils.sol**](/io-docs/introduction-1/soils/soils.sol.md). The physical properties of the soil govern the movement of water and air through the profile and have a major impact on the cycling of water within the HRU. 

The contents of nutrients and constituents in the soil are initialized using the file [**soil\_plant.ini**](/io-docs/introduction-1/initialization/soil_plant.ini.md), which references the files [**nutrients.sol**](/io-docs/introduction-1/soils/nutrients.sol.md) for the initial nutrient contents and the files [**pest\_hru.ini**](/io-docs/introduction-1/initialization/pest_hru.ini.md) and [**salt\_hru.ini**](/io-docs/introduction-1/initialization/salt_hru.ini.md) for the initial contents of pesticides and salts in the soil.