The first agricultural district in Northern Virginia, designed to protect farmland from the growing development in the county, has been approved by the Prince William County Board of Supervisors.

At a meeting last week, the supervisors approved the inclusion of 1,452 acres in the district. That land will be protected from local laws hampering farm operations, will be protected from land condemnations for public improvements and will be assessed at a lower tax rate than other properties.

The new district is in southeast Prince William County, adjacent to Quantico Marine Base. A second agricultural district, just a mile away, also has been proposed.

Under the new ordinance:

The county is prohibited from enacting any law that unreasonably restricts farming in the district, unless there is a clear threat to public health and safety.

Any development plans for land next to the district must ensure that the district is not threatened.

No condemnation or acquisition of land for public improvements, such as sewer and water lines or roads, can be approved if it would discourage agriculture in the district.

In addition, the district will come under the already existing land use assessment program, which allows land to be assessed on the basis of its use rather than its fair market value. The provision results in a significantly lower tax bill for landowners whose land is in the program.

County supervisor of assessments Ben Kelsey said that land under the program would be assessed at approximately 20 percent of its fair market appraisal.

County officials and farming groups in the county say that the land-use program has helped encourage continued agricultural land uses in the county.

Fred Fees, president of the Prince William-Fairfax Farm Bureau, and Prince William County environmental planner Makund Lokhande agree that the land-use tax break has helped slow the encroachment of subdivisions on farmland. Both say, however, that unless steps such as agricultural districts are taken, the future of farming in the county is bleak.

"There are 2,000 new houses a year built in Prince William County," said Lokhande. "That land is coming primarily from areas the county has zoned for agriculture."

Fees said he believed the new agricultural district would encourage county farmers.

"It's going to signify to the farmer that the county government is really interested in protecting his industry," Fees said.