PHOENIX (AP) - Conservationists want Arizona voters to decide this fall whether to amend the state Constitution to help preserve hundreds of thousands of acres of state trust land as open space.

An initiative drive formally launched Friday with a filing with the Secretary of State's Office is aimed at putting the proposed amendment on the November ballot.

Key elements of the proposal include setting aside some trust land to be conserved as open space without payment to the trust.

Additional acreage could be purchased for conservation at appraised values. Those values typically are less than prices paid at auction.

The state has 9.3 million acres of trust land. Revenue from sales and leases benefit schools and other public institutions.