The nominations where announced Friday morning via Twitter, reported Rolling Stone magazine.
Dierks Bentley, whose album Riser was both a commercial and critical success, follows his former touring partner Lambert with seven nominations, including Album of the Year and Male Vocalist.
In a twist, a tie in the latter category necessitated six - instead of the customary five - nominees. Jason Aldean, Luke Bryan, Eric Church, Brad Paisley and Blake Shelton join Bentley in the Male Vocalist race.
The ACM nominations are often distinguished by the inclusion of newer artists: Brandy Clark, with little radio airplay, is up for Female Vocalist of the Year, Brothers Osborne and Maddie & Tae compete in Vocal Duo of the Year, and the Cadillac Three appear in the Vocal Event of the Year category for their anthem 'The South.'
More From This Section
But it's the Entertainer of the Year category that best illustrates the ACMs' wild card reputation. Garth Brooks, who returned last year from a lengthy retirement, and Florida Georgia Line, who released just their second album in October, are both up for Entertainer, against perennial nominees Lambert, Bryan and Aldean.
Both the Entertainer category and the New Artist category winners are determined by fan voting.
The final three New Artist nominees will be announced later, with voting to determine the victor beginning a few days before the show.
The Academy of Country Music Awards will take place on April 19 at AT&T Stadium in Texas.