Napa County voters face a slew of decisions on Nov. 4, but only one county-wide ballot initiative: Measure P.

The measure seeks to extend for another 50 years voter-approved protections of the county’s Agriculture Preserve.

This week, two proponents of Measure P met with the Register editorial board: Save Measure J Committee Chairman Volker Eisele and committee member Ron Taddei. Both are grapegrowers and longtime advocates of conservation and agricultural protection policies in the county.

Measure P has garnered no formal opposition.

In a future editorial, the Register will state whether we support the measure and why. Here, we offer a summary of the measure and the views expressed by Taddei and Eisele.

If passed, Measure P would extend until 2058 the right of county voters to decide whether or not to approve proposed zoning changes in the Ag Preserve. This right was first granted in 1990 with a similar proposal, Measure J, which expires in 2020.

Since that measure passed, voters have decided the fate of several proposed zoning changes to properties outside of local cities yet within the vast Ag Preserve: Voters denied an effort to place tourist cabins near Cuttings Wharf, approved expansion of Bistro Don Giovanni in north Napa, rejected expansion of the old Pometta’s Deli on Oakville Grade, and approved changes at the Stanly Lane Pumpkin Patch.

Taddei noted that 2008 marks the 40th anniversary of Napa County’s Agricultural Preserve, the creation of which essentially assured the valley would remain planted to crops rather than condos, even as sprawl began to change the face of the Bay Area. Taddei said the spate of events this spring honoring the 40th anniversary spurred today’s preservationists to want to do something more to protect the county’s grapegrowing and wine-driven prosperity — and that something is Measure P.

Eisele said that while Measure J does not expire for 12 years, now is the time to extend it. “We still have an atmosphere here of a commitment to land protection,” he said, noting that an “older generation is slowly disappearing.” He said with the passage of time and with growth bringing new citizens to American Canyon, it is important to teach again the lessons of the last 40 years.

Measure P has three essential components.

• It extends Measure J’s voter controls through 2058.

• It requires a vote of the people to overturn an existing county regulation that requires a 160-acre minimum lot size in the Ag Preserve.

• It allows for an exception to the protections should the county need to convert agricultural land for affordable housing.

Eisele and Taddei explained that the time limit and the affordable housing exception were both written into the measure for legal reasons: If the law were made permanent or did not accommodate for state affordable housing mandates, it could be more easily be challenged or overturned in court.

Eisele said it is critical to keep decisions about the Ag Preserve in voters’ hands, so the law can’t be changed by a pro-growth majority of the Napa County Board of Supervisors.

“Napa’s legacy is just too important to be voted on by three people on a Tuesday morning,” he said.