PHOENIX - Conservationists and educators last week filed petitions to put an initiative overhauling management of state trust land on the November ballot, presenting voters with a choice between that measure and a referendum endorsed by the Legislature.

The state has 9.3 million acres of trust land provided by the federal government at statehood. Under the Arizona Constitution and federal law, the land and the income it produces must be used to benefit schools or other institutions.

Use of Arizona's trust land has been controversial in recent years as urban areas have grown into surrounding desert and forests. While conservationists have pushed for preservation of open space, developers seek access to property for building. Meanwhile, educators want more money for schools and ranchers fight to preserve grazing rights.

The competing interests now appeared headed for a ballot box showdown.

The initiative would add conservation as one of the requirements for trust land and set aside large tracts that could not be developed. It calls for approximately 694,000 acres statewide to be designated for conservation, would create new planning rules to boost income and create a new appointed board to oversee the Land Department's administration of trust land.

On Friday, supporters including conservation groups and the Arizona Education Association said they collected 301,000 voter signatures, well above the 183,917 signatures required to qualify the ballot. Election officials will check a random sample of the signatures to see whether enough valid ones were filed.

The legislative referendum, backed by groups representing ranchers and home builders, also would impose new planning requirements for trust land. The changes are designed to bring in more money for public schools, and allow the legislature to designate up to 400,000 acres in rural areas to be set aside for open-space conservation.

The Legislature also would create a process to set aside some or all of about 110,000 acres near urban areas. That land has previously been proposed or endorsed for conservation under a state program suspended for legal reasons.

Referendum supporters contend their proposal would better serve the trust's primary mission of raising money for schools and other public institutions and that the Legislature is best suited to make decisions about what land to conserve.