Salt, 29, returns to the club after initially joining during the 2018/19 season, making 11 appearances.
A former Sheffield United academy player, the centre-back has featured for the likes of Gainsborough, Stamford, Matlock Town and Worksop Town.
He will go into contention for Grantham Town's next fixture away at Boldmere St Michaels in the FA Trophy Second Qualifying Round.
Photo credit: Grantham Town
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