Tour organizers have moved four stops along the route of George Strait [ tickets ]'s country music festival from stadiums to smaller amphitheaters. The changes mean that the festival will not be an all-stadium affair for the first time in its three-year history.

Though promoters didn't state the reasons for the venue changes, sluggish ticket sales--or the prospect of slow sales--are often the cause of such moves. The tour opens in Tampa, Fla., on Saturday (3/24).

After tickets went on sale last month, the festival's March 25 stop in South Florida was moved from Pro Player Stadium in Miami to the Mars Music Amphitheatre in West Palm Beach. Pro-Player has a capacity of more than 42,000, while the amphitheater can hold a crowd of about 19,000.

This week, organizers announced that the tour's May 13 concert, which was to take place at the 70,000-capacity TWA Dome in St. Louis, has been moved to the 21,000-capacity Riverport Amphitheater in nearby Maryland Heights. In addition, a planned May 20 show at the Metrodome in Minneapolis has been scrapped in favor of a stop at the Post-Gazette Pavilion at Star Lake, near Pittsburgh. Finally, the tour's planned stop at the Route 66 Speedway in Joliet, Ill., has been moved to the New World Theatre in Tinley Park, Ill.

Besides the tour's namesake, the main stage bill for this year's Strait festival includes Alan Jackson, Lonestar, Lee Ann Womack, Brad Paisley, Sara Evans and Asleep at the Wheel.

Now heading into its fourth year, Strait's annual festival has played about 45 stadium shows to date and has grossed over $90 million in ticket sales alone, according to tour publicists.