# Soils

The physical soil properties are summarized in the file [**soils.sol**](https://swatplus.gitbook.io/io-docs/introduction-1/soils/soils.sol). 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.&#x20;

The contents of nutrients and constituents in the soil are initialized using the file [**soil\_plant.ini**](https://swatplus.gitbook.io/io-docs/introduction-1/initialization/soil_plant.ini), which references the files [**nutrients.sol**](https://swatplus.gitbook.io/io-docs/introduction-1/soils/nutrients.sol) for the initial nutrient contents and the files [**pest\_hru.ini**](https://swatplus.gitbook.io/io-docs/introduction-1/initialization/pest_hru.ini) and [**salt\_hru.ini**](https://swatplus.gitbook.io/io-docs/introduction-1/initialization/salt_hru.ini) for the initial contents of pesticides and salts in the soil.&#x20;