Desecrated Earth Mind Sludge discard no cards in hand discard from library?

[riolu]

what happens if i play Desecrated Earth or Mind Sludge and other player does not have cards in his hand can i tell him to discard from library?

[Twanos]

No, discard is only from the hand. If they have no hand then you can play the spells but they would just discard 0

[teletel]

There's no such thing as "discard" from library. Discard is always from hand. for library it will usually say to "Put" cards from your library in graveyard or out of play or something