Kelsea Ballerini teamed with Halsey to tape the 70th episode of CMT Crossroads at Nashville’s Ascend Amphitheater on Oct. 11. The new installment will air on March 25 at 10 p.m. ET. The cross-genre stars collaborated on each other’s hits, shared stories and more. While Kelsea, 26, has scored five No. 1 hits on the…