The Loudoun County Board of Supervisors, in a public hearing last week, delayed action on a draft plan to preserve farming and open space.

In sending the plan back to the Planning Commission for reconsideration, the supervisors said they wanted additional time to review several uncompleted studies of a controversial land planning program that is a major element of the draft plan.

The program, called transferable development rights (TDR), is designed to focus growth in urban areas and away from rural land. It would set up land owners' right to subdivide as a commodity that could be sold, without selling the land itself.

For example, a farmer could sell his development rights to a developer, who would use the purchased rights to increase the number of homes allowed on his urban property. In this way a farmer could reap profits from the development potential of his land, enabling him to continue farming rather than succumb to financial pressures by selling out. As a result, the farmer's land would no longer be subject to development.

Although urged by farmers and others to adopt the plan last week, members of the board said that information expected to come out of the TDR studies would justify the delay. Leesburg Supervisor Frank Raflo said he supported the draft plan, but said the "technicalities of getting a TDR established are such . . . that I feel this should be done right.

Board Chairman James F. Brownell said he wanted the rural plan to be adopted by a unanimous vote of the board, and the delay "is part of the process." Brownell and other supervisors supporting the TDR concept are optimistic that if the county can develop specific plans for implementation of the program it will have a greater chance to win favor from the three supervisors who last January voted against draft enabling legislation for the program.

Among the complaints registered by the three supervisors -- Catoctin Supervisor Frank Lambert, Broad Run Steven Stockman, and Sterling Supervisor Andrew R. Bird III -- were that the county's plans for implementing the TDR program were too vague.

The board wants to see some research by the planning staff on the technical aspects of the TDR program, such as standards for defining the areas from which development rights could be sold and areas where the purchased rights could be used to increase the number of lots allowed.

In addition, the Piedmont Environmental Council, a nonprofit organization that advocates preservation of open space, has done a market study for TDRs. The Coalition for Loudoun, comprised of local citizens, is working on a study of legal and administrative aspects.

County officials expect that clearer definitions of how the program would be carried out will improve the chances of gaining authority for establishing the program from the 1984 General Assembly.

Last year, the state legislators did not act on the proposed TDR legislation, but referred it to House and Senate committees for further study.

Before the board's vote last week, the supervisors were urged to adopt the draft plan by a number of speakers, including members of the planning commission and of the citizen's group that spent eight months formulating the draft.

John Adams, a member of the citizen's committee, told the board that the plan was "the most important thing you are going to have to consider in the next five years . . . if you fail to endorse this plan and move it forward there are going to be a lot of people . . . who will hold you responsible."

Among other proposals recommended in the draft plan is the hiring of a county agricultural officer. The officer would promote farming as an industry, in much the same way the county's department of economic development works to attract new business and industry. Additional duties would include educating nonfarmers about the economic benefit farming brings to the county, and providing farmers with agricultural, tax, and other information.

In other action at last week's public hearing the board:

*Placed proposed amendments to the county's dog ordinance on the agenda for action Sept. 17.

The proposed amendments, offered by Supervisor Stockman, would require that any dog that, without provocation, bit a person for the second time while not being kept under restraint by its owner, would be ordered destroyed.

Currently, the county ordinance provides that any dog proved to have killed livestock would be ordered destroyed, but does not provide for cases in which dogs bite humans.

*Placed on the Sept. 17 agenda for action are proposed amendments to the nuisance ordinance that would broaden the definition of "nuisance" to include tall leaves and grass, junk accumulation, and conditions that attract rodents. The proposal would give the county wider authority to control these conditions. Farmland would be exempt unless "negligence or improper operation" of the farm were found to be a cause of nuisances.