Would clothes be deemed as ritually impure after touching dry najasat?
Clothes and the place where prayer will be established need to be clean in order for the prayer to be valid. Therefore, as the dried najasat on clothes or body prevents one from establishing prayer, so they need to be cleaned. However, if the dirt only touches but does not leave mark on the clothes, one may establish prayer.
Source: Presidency Of Religious Affairs The Turkey, High Board of Religious Affairs FATWAS