CARRIE IS DOWN ON HER FARM!

Owning a farm was a no-brainer for Carrie Underwood, who grew up on one in Checotah, Okla. A self-described green thumb, the country star, 42, lives on 400 acres with her husband, former NFL player Mike Fisher, and their two young sons in Tennessee.

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But a source tells Star the constant grind of farm life is beginning to wear on the "Before He Cheats" singer. "It's become too much for her to maintain, and she's getting no sleep because she's up at the crack of dawn taking care of all these animals," says the insider of the chickens, horses and sheep on the property, which also inc