Greene, who missed last season due to academic issues at a junior college, scored on a 1-yard plunge on the Hawkeyes' first possession, capping a 69-yard drive, and Iowa was on its way to an easy win.
The Hawkeyes overpowered the Black Bears (0-1) with 245 yards rushing, including a 19-yard TD run by Hampton on his first career carry.
Iowa led 22-3 at halftime and turned the game into a blowout in a 15-second stretch early in the fourth quarter. Paki O'Meara capped a 10-play-drive with a 1-yard run to make it 32-3, and after an interception by a Pat Angerer, Hampton scored to make it 39-3 with 14:43 left.
Hampton added a 22-yard TD run with 3:29 left, and finished with 68 yards on nine carries.
Jhamal Fluellen ran for 104 yards to lead Maine, which lost its fourth straight to a Football Bowl Subdivision team after winning at Mississippi State 9-7 in 2004. The 43-point loss was Maine's worst in seven meetings against FBS opponents.
Christensen started all 12 games in 2007 and had a tenuous hold on the No. 1 job after fall camp. Stanzi came in after Christensen threw a second-quarter interception, but Christensen bounced back in the second half, helping the Hawkeyes put the game out of reach.
Christensen was 9-of-15 for 122 yards, with one touchdown and one interception. Stanzi was 9-for-14 for 90 yards, playing most of the second quarter and re-entering the game in the fourth quarter.
Iowa's Bradley Fletcher came down with the interception off a tipped ball the first time Maine got the ball, and Christensen found Brandon Myers for a 4-yard touchdown pass to make it 14-0 with 3:37 to go the first quarter.
Christensen was 5-of-9 for 60 yards in the first half. But when he missed, he missed badly -- including an underthrow to Paul Chaney Jr. that Maine picked off at its own 3.
A.J. Edds bailed out Christensen with a safety that made it 16-0 with 12:31 to go in the second quarter, but Stanzi got the call for the rest of the half. He led the Hawkeyes to a pair of field goals to push Iowa's lead to 22-0.
Maine's Bryan Harvey hit a 40-yard field goal as half ended for the Black Bears' only points.
Adam Farkes was 9-of-22 for 83 yards and two interceptions for Maine.
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Ohio State quarterback Cardale Jones was taken to a hospital Wednesday night and treated for a severe headache, according to multiple media reports.
The Florida Gators will start Treon Harris at quarterback in Saturday's opener vs. New Mexico State over redshirt freshman Will Grier, coach Jim McElwain said Tuesday.
Baylor University has hired a Philadelphia law firm to independently investigate the university's handling of sexual assault complaints, including one against defensive end Sam Ukwuachu.
Oregon State and former coach Mike Riley face a federal Title IX lawsuit filed by a woman who said she was raped as a result of the coach's failure to correct a sexually violent culture.
James Madison players will wear decals on their helmets during Saturday's season-opening game in memory of the two journalists who were killed during a live television broadcast.
Los Angeles prosecutors have charged a man in connection with the theft of the University of Southern California's copy of O.J. Simpson's Heisman Trophy more than 20 years ago.