A proposed citizens' initiative to conserve at least 570,000 acres of state trust land is drawing outrage and applause as longtime foes prepare to face off once again.

Backers of the measure won a key ally last week when the Sierra Club's Grand Canyon Chapter voted to support the plan.

"We think it's a pretty clean proposal," said Sandy Bahr, the club's outreach director. "We think important lands are conserved, and there is a process for preserving additional lands. That is important as communities grow."

For a constitutional amendment to make the Nov. 4 ballot, advocates must collect 230,047 valid petition signatures by July 3.

The Sierra Club withheld its support in 2006 when conservationists put a similar, more complex measure on the ballot.

Like the 2006 proposal, the new one would reform the way the state handles 9.2 million acres of trust land that the federal government gave Arizona statehood in 1912.

The home-building and cattle-ranching industries - the same opponents who scuttled a land-reform measure two years ago - are lining up against the new initiative. Opponents jumped on a key component of the plan, the immediate conservation of 570,000 acres of what proponents identified as some of Arizona's most environmentally sensitive lands.

The Arizona Constitution now mandates that state trust land be sold or leased at auction to the highest bidder, with funds going to schools and other public agencies.

"We will definitely work against this," said state Sen. Jake Flake, R-Snowflake. "I don't like the idea of giving away half a million acres of land for free. This could make a difference for (Arizona) being the last in funding for (educating) our kids. . . . I am very disappointed."

Flake had bargained in recent months for a less sweeping referendum with Gov. Janet Napolitano and a small group of legislators. Negotiations recently stalled.

Bahr and other supporters said the new initiative is simpler than Proposition 106, the land-reform measure that narrowly failed in 2006.

Along with land preservation, it would allow the Arizona State Land Department greater flexibility to plan and manage sales. The measure would also allow the state to appraise the value of some land for conservation and sell it for preservation without going to auction.

Napolitano's proposed referendum would not have allowed any land to be preserved without cost, a concession she had made to cattlemen, home builders and other potential foes.

Flake blamed the governor for the breakdown in negotiations and said Napolitano gave up the effort after talks reached an impasse.

Napolitano spokeswoman Jeanine L'Ecuyer said the governor never walked away.

"It was very clear that some parties were unwilling to move on some key issues," she said, adding that Napolitano now supports the initiative effort.

John Wright, president of the Arizona Education Association, said his group would support the effort. By allowing the Land Department to plan and manage the land's sales and development, the value of all land will rise, he said.

"This is pretty specific planning language," Wright said. "The Land Department will work with towns, municipalities, counties and developers to plan for best use of the land. So, we'll end up with better growth and a better revenue stream for the classroom site fund."

Advocates have long argued that preserving some pristine sites would bring higher value to nearby land. Homeowners typically pay a premium if the acreage surrounding their home will never be developed. This would negate any drain on the education fund if the state takes some land out of the auction cycle, proponents say.

The Arizona School Boards Association, however, is worried about the long-term cost of conserved land.

"The concern lies in both ensuring we receive money for education and also whether we will have to pay to manage it," said Janice Palmer, lobbyist for the association.

Cattlemen and homebuilders' associations generally oppose free land for conservation.

"Giving away public land for free has always been a problem for education," said Spencer Kamps, vice president of the Home Builders Association of Central Arizona.

Even if voters approve the initiative, Congress would have to amend the federal law that made Arizona a state.