OLYMPIA – An initiative that targets property rights appeared headed for the statewide ballot after sponsors hauled signed petitions to the Capitol on Thursday.

Backers of the measure, Initiative 933, applauded as a shiny, green 1950s John Deere tractor and small trailer loaded with petition signatures, hay bales and campaign supporters pulled onto the Capitol sidewalk.

Steve Appel, president of the Washington Farm Bureau, said the campaign had support from more than 315,000 voters – enough to meet the minimum required by the state, with a healthy cushion for duplicate or invalid signatures.

I-933 would require state and local government agencies to compensate private landowners for regulations that harm the value of private property.

Some farmers say that without such a change, government rules will continue to unfairly remove valuable farms and ranches from production.

Oregon voters passed a similar measure in 2004, but I-933 differs in part because it does not affect land use and zoning regulations in effect before 1996, Farm Bureau spokesman Dean Boyer said.

“It’s really in the past 10 years when we’ve seen an exponential increase in government regulations,” Boyer said.

Opponents of I-933 also gathered on the Capitol steps, skewering the measure as an unnecessary gutting of important environmental rules.

In Seattle, a measure opposing the NBA SuperSonics’ push for stadium improvements and a new lease also looked like it could qualify for a citywide vote.

That measure, Initiative 91, requires the city to make money on any leases of public property to professional sports teams. The Sonics’ owners, who have threatened to move or sell the team if they do not get a new deal for KeyArena, want about $220 million in improvements and an end to the present profit-sharing lease with the city.

Campaign spokesman Chris Van Dyk, of the group Citizens for More Important Things, handed in more than 20,000 signatures on Thursday. About 17,700 signatures from registered Seattle voters are required to qualify the measure, and the actual deadline isn’t for several more months.

Meanwhile, another pair of initiative campaigns had appointments with state elections officials today, and at least one was optimistic about making the ballot.

Initiative 921 would send some sex offenders to prison for life on a first conviction. Sponsor Tracy Oetting of Skykomish declined to reveal her signature count Thursday, but said she was confident the measure would make the ballot.

The remaining question, she said, was how large a cushion the measure would get with signatures still pouring in on Thursday.

Initiative 946 also had an appointment with Secretary of State Sam Reed’s office today. The measure would require state and local governments to verify the identity and immigration status of every applicant for nonfederally mandated public benefits, including welfare, Medicaid, food stamps and public housing.

The state’s foremost initiative promoter, Tim Eyman, submitted stacks of voter signatures last week – more than 252,000 by his count – for his third measure aimed at capping car tab fees at $30.

He planned to turn in additional signatures by today’s deadline.

Last month, Eyman failed to gather enough signatures to force a vote this fall on the state’s new anti-discrimination law for gays and lesbians.

Critics of Washington’s estate tax also appear poised to secure a November ballot spot for their initiative to repeal the tax. Sponsors of Initiative 920 announced last week that they had submitted an estimated 300,000 voter signatures.