Here the highway has been widened and the concrete laps closer to the cornstalks. There the shopping center sprawls across the pasture where the cattle once grazed. In still another spot, Southern suburban singles splash in the apartment complex pool sunk in the middle of a former cotton field.

"That's why it's such a difficult thing for anyone to get a handle on -- it's very incremental," said Bob Gray, director of the National Agricultural Land Study. The federal task force, headed by representatives of the Agriculture Department and the Council on Environmental Quality, was formed when the Soil Conservation Service noticed how fast those increments were adding up and federal officials began worrying about what it portended.

Oh, when them cottonfields get paved over, you can't pick very much cotton.

A 1977 inventory of agricultural land found that the rate at which it was being converted to nonagricultural uses had picked up markedly. Over the 10 years surveyed, it had been slipping away at a rate of almost 3 million acres a year.

Particularly hard hit have been some of the more clement states where the same conditions that make the states major producers of winter vegetables also produce more pressure for development.In Florida over 10 years, 3.5 million acres of agricultural land -- nearly 15 percent of the state's agricultural base-- were lost.

Deciding what to do about shrinking farmland includes evaluating other factors as well, said Gray. Those issues include "how much demand will be there in the future for exports -- and it looks like that's going up," he said. "And how much productivity increase can we get in yields? Some analysts believe that yields have leveled off.

"We're chipping away at the base everyday in land being converted," he said. Additional land is being lost to serious soil erosion because of intensive cropping being done to meet the demand for exports.

"When you put it all together, some of the scenarios can be disturbing," Gray said.

Like any commodity growing increasingly scarce, the phenomenon of America's shrinking agricultural land has produced a variety of interests with different ideas about what to do with the bit that's left.

Some of them are investors with gleams in their eyes. Some of them are family farmers and their advocates with heightened fears about the consequences of separating ownership of the land from cultivation of it. Others are government officials concerned about how far to intervene in land-use questions. Still others are conservationists.

"The National Agicultural Land Study and other examinations of the issue finally led us to the conclusion that there is a need to focus public attention on the loss of farmland as a serious conservation issue," said Douglas P. Wheeler, director of a new group called the American Farmland Trust.

Modeled along the lines of nature conservancies (into which owners put their land to preserve it as it is for the future) and funded by the Conservation Foundation and the Rockefeller Brothers Fund, American Farmland Trust is set up primarily to advise state and local groups about how to protect agricultural land.

Several groups and many state and local agencies already are actively working to save fields and pastures for agricultural use. The Massachusets Farm and Conservation Land Turst, for instance, acquires development rights on farmland for resale to the state. The title to the land remains with the farmer, who can sell the land but with restrictions on how it may be used.

"There are probably 48 states with some kind of program aimed at retarding development of farmland," Wheeler said. Some states provide tax concessions for agricultural use. Others provide for acquisition of development rights. Others protect farms by zoning.

While Wheeler's group has focused on agricultural land as a conservation issue, other groups have formed out of concern over the ownership of this increasingly valuable commodity. In some sectors, including among some farm groups, ownership of farmland by agribusiness corporations has always been an issue. Now a new concern has arisen about speculative investment in farmland by pension funds, foreigners and other groups.

Part of the concern has focused on the American Agricultural Investment Management Co. (AAIM), which has been described as proposing to act as an investment management agent to locate and buy agricultural properties for pension fund clients. The properties would be farmed by tenants or farm management companies.

Rapid apprecition in farmland values, driven by inflation, have helped make farmland an attractive investment. "In addition, there are growing perceptions on the part of the public and investors that in the 1980s there will be greater pressure on the food supply, increasing prices of food, increasing scarcity of farmland and . . . further rapid increases in the price of farmland," said Susan Sechler, deputy director of the Argriculture Department's office of economics, policy analysis and budget.

Sechler opposed persion fund farmland investment plans at a hearing by the Senate Select Committee on Small Business. "The working farmer is dependent on the earning capacity of the farm on a current basis," she said. "He is at a disadvantage in bidding on new or additional land in competition with nonfarm investors who are looking to future capital appreciation rather than operating returns."

According to Sechler, "farmers, whose major tool is equity and whose incentives for buying farmland are connected with long-term productive activity, would be competing with cash-paying investors whose interests are more narrowly concerned with short-term profit." She added that the Agriculture Department is "also concerned about the possible effects on local communities of substantial ownership of farmland by investors so far removed in every way from those communities."