U.S. agriculture policy, in the pursuit of possibly mythical efficienty, has driven thousands of small farmers off the land and stranded them in urban misery or rural poverty, according to a major study conducted in part by Labor Secretary Ray Marshall before he joined the Cabinet.

This decades-old-policy, practiced in Republican and Democratic administrations alike, has exacted a disproportionately harsh toll on small farms in the South, particularly black-owned ones, the study says, as farm, tax, credit and research programs advanced large and corporate farms.

"The present agricultural system is dominated by certain actors who attempt to maintain control primarily for their benefit," conclude Marshall and Allen Thompson, an economics professor at the University of New Hampshire.

"The controlling figures in this system large farmers and their organizations, the U.S. Department of Agriculture, the land-grant college system, food processors, agricultural equipment dealers,key congressional representatives and senators) share certain values about how the system should operate and for whose benefit."

The basic premise that large-scale farming is more efficient in that it produces more low-cost goods is challenged by the two. They say the traditional view has avoided the costs of research, lost taxes, energy consumption and environmental damage in determining efficiency, and has overlooked the costs of welfare, unemployment, crime and the urban decay resulting from a displaced population.

"One of the greatest tragedies in the past several decades," Marshall and Thompson say, "was the large-scale displacement from agriculture of people ill-prepared by education training or experience for nonfarm jobs. Clearly this has resulted in increased urban congestion, with all its associated problems and costs, as well as widespread poverty and unemployment in rural areas."

Their report, "Status and Prospects of Small Farmers in the South," was prepared for the Southern Regional Council, a private organization seeking to eliminate racism and poverty.

The study was completed late last year while Marshall was director of the Center for the Study of Human Resources and professor of economics at the University of Texas in Austin. It was released last week.

Small farms are considered to be those selling $5,000 or less in farm goods a year. Nationally, 966,631 such farms accounted for 26 per cent of the 3,704,912 farms in 1959. By 1969 they accounted for about 21 per cent (587,668) of the nation's 2,728,139 farms. More than one-half of the small farms are in the South.

"Small farmers have borne the major brunt of the changes in the farming sector," Marshall and Thompson write, and thus "the South has experienced a major displacement from farms and can be expected to experience future changes if past trends continue . . . Without significant changes, few nonwhite farmers are likely to survive in Southern agriculture."

They recommend a series of major changes in U.S. farm policy, but so severe is their view, they say, that "since the U.S. Department of Agriculture shows so little interest in small farmers, all federal programs designed to improve the conditions of small farmers should be removed from the department and placed in a separate agency . . ."

Specifically, they criticize:

Farm research, much of it carried on at land-grant schools with public money, that has focused on crops, livestock and machinery not geared to small farms, but which instead increased the acreage required for optimal operation.

Credit practices, even among such federal agencies as the Farmers Home Administration and the Bank for Cooperatives as well private banks that have been reluctant to make loans to small-scale, more marginal farms.

Technical services that have been provided to larger farmers by county agents but not to smaller ones, have, Marshall and Thompson say, met with hostility at worst and lack of concern at best: They note that Mississippi got its first black county agent in 1975 and only as the result of a court suit.)

Tax policies that have, in effect, provided land and equipment subsidies to well-heeled nonfarmers seeking tax write-offs and to large farms able to carry expenses or buy land at inflated values.

Marketing trends that have seen the emergence of fewer but bigger purchasers of farm goods , thus leaving "severe competitive disadvantage when dealing with the large agribusiness concerns."

Marshall and Thompson clain that the federal programs since the New Deal that were intended to help small farmers with limited resources have been twisted to enhance bigness. "The banks for cooperatives," they write, "established in 1933 because established cooperatives were having difficulty obtaining credity from traditional sources, continued to benefit wealthier co-ops by providing both credit and technical services but have not proved to be a ready source of credit to low-income co-ops."