Nashville, Tenn. ? The last time Willie Nelson had a No. 1 hit was back in 1989, when George Bush was president.

Fourteen years later, there’s another Bush in the White House, and Nelson is back on top of the charts — this time with “Beer for My Horses,” a No. 1 duet with Toby Keith.

Nelson’s reappearance proves a hard truth about the country music business: It’s nearly impossible for veteran stars to get radio airplay unless they’re hitched to a younger star.

“Country radio is looking for the next hot thing, and I don’t think they have a lot of patience to give an opportunity to an act whose real heyday has come and gone,” said Neil Pond, editorial director for Country Music Weekly magazine.

The last two high-charting singles for George Jones were duets with younger stars: “You Don’t Seem to Miss Me” with Patty Loveless in 1997 and “Beer Run” with Garth Brooks in 2001.

Dolly Parton’s last No. 1 was a duet with Ricky Van Shelton in 1991. And back in 1988, Buck Owens had his first No. 1 song in 16 years with Dwight Yoakam on “Streets of Bakersfield.”

“It’s part of the shame of country radio that there’s not more of a place for these artists,” Pond said.

Lee Logan, program director for WSM-FM radio in Nashville, said country music radio was just playing what people wanted. The play lists represent changing tastes — not an aversion to older artists.

Toby Keith, left, and Willie Nelson share a laugh during the video shoot for their duet Beer

“If you’ve been an artist for 30 or 40 years, you have a style you’re comfortable with, and sometimes you’re just not on the cutting edge anymore,” Logan said.

But Logan acknowledged that many veteran acts now record for small, independent labels that don’t have a lot of promotional muscle.

Nelson and Keith weren’t the only pair to produce a cross-generational hit this year. “It’s Five O’Clock Somewhere” by Jimmy Buffett and Alan Jackson went to No. 1 and was Buffett’s highest-charting single — country or pop — since “Margaritaville” in 1977.

Marty Stuart recorded a duet and video with Merle Haggard called “Farmer’s Blues” that began airing this month. Haggard hasn’t had a No. 1 hit since 1988’s “Twinkle, Twinkle Lucky Star.”

“What it really gets down to is the song,” Logan said. “Take ‘Beer for My Horses.’ Could there be anyone more perfect to sing that song with Toby Keith than Willie Nelson?”

Keith thought the same thing when he was writing the second verse, which celebrates frontier justice:

“Grandpappy told my pappy, back in my day, son, a man had to answer for the wicked that he done. Take all the rope in Texas, find a tall oak tree, round up all of them bad boys, hang them high in the street for all the people to see.”

Keith knew that Nelson had been in western movies, and thought he would be perfect to sing the second verse.