Montgomery County inaugurated the nation's newest farmland preservation technique last week when it approved the use of transfer of development rights (TDRs) from a Poolesville turf farm to a town house development near the Prince George's County line.

The Montgomery County Planning Board unanimously approved preliminary plans for a 262-unit town house condominium project in the Fairland section of eastern Montgomery, along Columbia Pike, using 87 TDRs purchased from the Summit Hall Turf Farm on River Road Extended, near the Potomac River in western Montgomery.

The town house developer, the Artery Organization Inc., apparently is paying $4,750 for each TDR, or just over $400,000 in all, according to preliminary documents filed with the county. They will enable the company to construct about 100 more houses on the 38-acre site than would be permitted under existing zoning.

Artery officials said the increase in the number of town houses they will be able to build should result in lower prices. They hope to sell their town houses for $85,000 and up, "$10,000 less than than the typical three-level town house in this area."

The Montgomery County TDR system, the first large-scale use of TDRs in the nation, is one of several methods developed by the county and state in the past 30 years to help preserve the dwindling supply of Maryland farmland. The state was the first, back in the 1950s, to provide preferential property tax treatment for working farms, and recently established a fund to buy perpetual agricultural easements. Under this program, farmers receive a lump payment to ensure that their farms are never subdivided for housing developments.

The new county TDR system works, in effect, like cluster zoning, permitting more intense development in some designated "receiving areas," like Fairland, in exchange for restricting development in rural areas.

It was established after the County Council voted in 1979 to preserve rural areas by "downzoning" them, changing the minimum house lot size from five to 25 acres. The council then asked planners to design an equitable way to compensate farmers for the lost development potential of their property.

Unlike other farmland preservation programs, the TDR system compensates the farmers at no direct public cost by allowing them to sell TDRs to developers who can use them to increase housing densities in some built-up areas. The landowner can sell one TDR unit for for each five acres.

Although there was local opposition this spring when the county designated Fairland and parts of eastern Montgomery as "receiving areas," where more intense development can take place, there was no opposition to last week's first TDR project.

Planning board members hailed the project, not only for helping to preserve county farmland but also for providing an incentive to developers to construct badly needed housing in the county.

The board also noted that Artery, the first developer to use TDRs, is not planning to make maximum use of the increased density allowed with the TDRs. Artery could build 319 town houses, or 8.4 units per acres, according to county planners, but will construct only 262, or 6.9 units per acre. Under present zoning, without TDR credits, only 164 units would be allowed on the site. The houses will be clustered and the rest of the site will be used for open space, a swimming pool, tennis courts and a soccer field.

Planning Board Chairman Norman Christeller said the Artery project is an expression of business community confidence in the new TDR program. "What it means is that there will be perpetual easements on 435 acres of land at the Summit Hall Turf Farm , restricting it to agriculture and open space . . . and achieving the purpose" of the farmland preservation program, he said.

The turf farm, the nation's first, was started in Gaithersburg after World War II by William H. Wilmot, and later acquired farmland along the Potomac off River Road. The money the Wilmot family will receive for its TDRs will buy a new tractor and help the family consolidate its grass-growing operations on River Road, according to the family firm's attorney, Clyde Winters.

The Artery project is opposite the Greencastle Country Club, where the planning board approved an 813-unit housing project two weeks ago. The country club is within the Fairland TDR receiving area, but initial plans do not call for using TDRs to increase the density of the development, county planners say.

A larger subdivision of 2,032 garden apartment units, on nearby Robey Road just outside the TDR area, and a new shopping center on Columbia Pike also are under way in the Fairland area.