The only true opposite of salty is not salty. You can contrast salty with sweet or bland, but these words are not 'opposites'.Would you please tell me what the opposite of 'salty' is? Could 'bland' be a choice? Thanks.
"Salty" is one of the five main tastes which food can be sorted into. They are salty, bitter, sour, sweet and umami. Therefore, salty doesn't have an opposite, as the other said, except "not salty" which isn't really a description of a taste, simply a description of what a taste is not.
You just have to say that it needs more salt.Then what's the appropriate word/phrase describing something that needs more salt? You're having this soup and you believe it should have much more salt in it.