Since the tide of development began to sweep into once-sleepy, agricultural Loudoun County in the mid-1960s, two visions of Loudoun's future have been in conflict. To many, it seems as though a line has been drawn down the middle of the county.

To the west lies the rich farmland on the foothills of the Blue Ridge Mountains. To the east sits the rapidly growing commercial and residential area around Dulles International Airport. At odds countywide are the desire to preserve open land and the push for development.

It is from an attempt to reconcile this clash over what will become of Loudoun that one of the most controversial land-use proposals in years has arrived on the county's political agenda: transferable development rights.

For now, the debate over the novel concept seems only to have made the divisions in Loudoun deeper.

"I have had more constituency phone calls on this issue than I have on any other issue since I have been on the [county] board," said Supervisor Andrew R. Bird III (R-Sterling).

If approved, the measure would allow a landowner to sell the development rights to his or her land without actually selling the land. A farmer, for example, could sell the right to develop his land to a builder. The builder then could use those development rights on land he owned elsewhere in the county to build there at a higher density than would be allowed under ordinary zoning rules.

In turn, an easement -- a permanent restriction on development -- would be placed on the farm land, requiring that the land remain open space "in perpetuity."

Supporters of the transferable rights, which the Loudoun Board of Supervisors is expected to vote on in the fall, say the unorthodox concept would give the county the best of both worlds: a chance to target development in areas of the county where roads and sewers already exist, while protecting the county's agricultural areas from being snuffed out by this same development.

"It's the old line of 'have your cake and eat it, too.' [TDR gives] us the chance to do that," said Supervisor James F. Brownell (R-Blue Ridge).

Opponents of the idea call it a Rube Goldberg device that would cost the county money, lower the quality of life in eastern Loudoun and even hurt the farmers whom the TDR concept is intended to save.

"This is a creative aberration of a bureaucratic government," said Bird.

Since the transferable development rights first were proposed last year in a document called the Rural Land Management Plan, the concept has politicized the county in unexpected fashion.

One reason is the bitter history of an experiment in "density transfer," a concept similar to TDR, at the Countryside housing development near Dulles.

In that action, which was approved last fall by Loudoun's supervisors, Countryside's owner, 437 Land Co., paid more than $500,000 to a farmer in the western portion of Loudoun County. In return for a permanent easement on the farmer's land, the board allowed the developer to add 112 housing units to the 2,540-unit Countryside complex.

A citizen group from Countryside is suing the supervisors to try to stop the transfer, which it contends will crowd the development and lower the quality of life and property values.

To Brian Bell, president of the Countryside Citizens Committee, the density transfer experiment and the proposed TDR legislation are raw deals.

"It basically involves taking something away from our community and giving it to someone else in the county," said Bell.

But supporters of transferable rights say that protecting open spaces in some portions of Loudoun is worth some extra crowding in others.

"Agriculture is part of what Loudoun County is about. If you take it away, you lose the character of Loudoun County," said John Sleeter, owner of Hill High Orchards in Round Hill and a supporter of TDR.

Board chairman Frank Raflo (D-Leesburg), also a strong supporter of TDR, argues that agriculture has spurred Loudoun's recent development, including the multibillion-dollar Xerox Corp. commercial and residential development project currently under way.

"Developers come here for the cows, not the condominiums," said Raflo. "They like the open spaces."

But Bird countered: "Frank Raflo ignores the fact that development isn't going to occur out in the west anyway."

Transferable development rights will merely reduce the county's ability to win concessions from developers in return for zoning changes, Bird charged.

If a developer has already purchased a TDR to increase the zoning density on a property, Bird said, the developer will not be willing to build roads, sewers or other "proffers" that the county traditionally exacts before approving development projects.

"The developer will say, 'I've already paid my share.' The taxpayer will end up paying for the capital improvements this county needs," Bird said.

Another aspect of TDR that opponents frequently attack is the notion that development could be prohibited on a piece of land "in perpetuity."

Supervisor Steve W. Stockman (R-Broad Run), an opponent of TDR, said that the concept of perpetuity runs counter to traditional philosophies of law in the county and invites legislative and legal nightmares in the future.

"What does perpetuity on these things really mean? No one can define it," he said.

Opponents also maintain that the group that could be hurt most by TDR is the very group some are trying to help: the farmers.

A financially strapped farmer who sold the development rights would get "fast money," Bird said, but if, in the future, the farm still proved unprofitable, the value of the land would be greatly diminished because of the restriction on development. Once a farmer has sold the development rights, construction on the land is restricted to one house for every 50 acres.

Carroll Laycock of Farm Credit Services in Leesburg said he supports TDR as an option for farmers, but he agreed that there is a danger that some farmers would sell their development rights imprudently.

After a farmer sells the rights, Laycock said, "He's got the dirt and that's it."

Sleeter, however, said that the dirt alone might be enough for farmers who want to benefit from rising land values in Loudoun County yet still pass on the family farm to the next generation.

"They give older farmers the chance to realize some revenue out of their land after years and years of hard work they have put into it. They get the cash dollars and still retain ownership," said Sleeter.

With the supervisors returning from a summer recess on Aug. 21, the politics of the TDR plan is taking on a special urgency.

A bill passed in this year's session of the Virginia General Assembly enabling Loudoun County to draft a specific TDR proposal stipulated that any TDR bill must be passed by the legislature by July 1, 1986.

This means that in order for the legislature to act on a TDR proposal during its winter session, the Loudoun board will have to approve a TDR measure this fall.

Opponents concede the likelihood that a TDR program will be approved by the board this fall, although haggling is expected on details such as how large a farm must be to participate in the program. But the fate of TDR in the state legislature, which is conservative on land-use issues, is less certain.

Only a few jurisdictions in the country have implemented TDR programs.

Montgomery County is one, and four years' experience there with TDR has not quelled debate. A court challenge, seeking to block development of a $7 million golf course and 850-unit housing complex on Avenel Farm near the Potomac River, was rejected last month by a Maryland state judge who upheld the TDR concept.

The novelty of the program ensures that "serious reservations" will be raised if a TDR measure goes to the Virginia legislature, said state Sen. Charles Waddell (D-Loudoun), a supporter of TDR.

Also adding urgency to the task of TDR supporters is their perception that they are mounting their last stand in Loudoun County before the political balance on the board shifts against them.

Supervisor Stockman has been pushing to redistrict the county in 1986. If that happens, as expected, it is likely that the eastern portion of Loudoun will gain greater representation, casting doubt on the prospects of transferable rights and the pro-farming political agenda in general.

Already, there is a feeling among many in eastern Loudoun that the county is doing more than it can afford to support farming.

The land-use tax, for example, gives preferential tax treatment to farmers, who pay at a lower rate than nonfarmers. In a recent survey of Loudoun farmers conducted by Raflo, 84 percent said that their farms would be in danger of failing if the land-use tax break is taken away.

But, according to Bird: "If this county gets [TDR], the land-use tax is in definite jeopardy. They can't have both."

"Agriculture is treated like the supreme goal of the county, and that's not true," continued Bird.

Statements such as this frighten Raflo. If agricultural interests cannot accomplish the main items on their agenda soon, he said, farmers "will be outnumbered, outvoted and probably out of business."