The largest laboratory in the nation, and possibly the world, devoting its time exclusively to human nutrition is in Grand Forks, N.D. (population 41,000).

Why? Because Sen. Milton R. Young put it there. The North Dakota senator is the ranking Republican on the agriculture appropriations subcommittee, where he has sat for 31 years and which he chaired for two years when the Republicans last held a majority in the Senate, in 1953 and 1954.

"The man responsible for this laboratory is Milton R. Young," said Thomas J. Clifford, president of the University of North Dakota, where the laboratory is. "He has done much for agriculture, not only for North Dakota, but for the entire nation as well."

But mostly for North Dakota.

A year ago, Young maneuvered $3.5 million into the Agriculture Department's budget to put a new wing on the seven-year-old nutrition lab at Grand Forks. Oddly enough, the senator was able to win approval for the new wing just after the White House ordered a moratorium on all Agriculture construction.

There is nothing new and certainly nothing illegal about the congressional pork barrel, but it is normally asssociated with hundred-million-dollar defense and water projects. Rarely, if ever, has the pork barrel been identified with things like a human nutrition laboratory with an operating budget of $1.6 million a year. But pork comes in all shapes and sizes, not the least of which is the Agriculture Department's $330 million-a-year research budget.

The 12 members of the Appropriations subcommittee represent 11 states, all but two of which could be called farm states.The obvious exception is Alaska Republican Ted Stevens. Less obvious is Majority Leader Robert G. Byrd, from coal-producing West Virginia.

A few years ago, Byrd got the Agriculture Department to open what is known as the Soil and Water Management Laboratory on the campus of West Virginia University in Morgantown.

The lab's budget is only $415,000 a year but it is so deep into the research of how to reclaim and revegetate coal land scarred by mining that the budget is expected to reach $1 million next year. Agriculture sources say that in five years the lab will be big enough to serve as the national model for all coal-producing states wanting to reclaim their land.

Of the 11 states represented on the Senate Appropriations subcommittee, only Alaska does not have a major agricultural research facility. The other 10 states have more than 30 laboratories doing more than 30 percent of the farm research in the United States. More significantly, these 10 states won far more than a fair share of the farm research dollars in the last five years.

In the last two years, Agriculture closed down 10 laboratories in economy moves, but only one (in Quincy, Fla.) was in a state represented by a subcommittee member. Agriculture more than made up for the Florida closing by putting four of its 11 new labs in Florida. Two of the remaining seven were opened in states (West Virginia and Oregon) represented by subcommitte members.

"Why do we put labs in those states?" an Agriculture Department official asked. "Because there's political clout to put them in those states. If their constituents say it's to their advantage to have one there, well, by God, they're going to have one there."

Take subcommittee member William Proxmire, whose home state of Wisconsin produces 17 percent of the milk, 24 percent of the butter and 37 percent of the cheese in the country. Proxmire has chafed for 15 years that the United States had no national laboratory devoted to research on dairy forage (what cows eat).

He won't be chafing any longer. He got the Agriculture Department to spend $1.1 million this year planning the Dairy Forage Research Center, whose first greenhouse will be built on the campus of the University of Wisconsin at Madison.

"This isn't a defense project or a water poject and it's not going to a big corporation," Proxmire said in defense of the project. "Besides, all indications are that this laboratory will have an overwhelming benefit to-cost ratio. We project it will have a 100-to-1 benefit to-cost ratio."

Depsite the White House ban on Agriculture Department construction projects, Sen. Birch Bayh (D-Ind.), another member of the Appropriations subcommittee, got the department to commit itself to building a $4 million National Soil Erosion Research Center. There are four other states besides Indiana in the Corn Belt but not only did Bayh get the erosion research center for his home state, he got it for Purdue University, which he attended.

No one on the subcommittee has worked harder for his state than has Sen. Lawton Chiles (D-Fla.), who this year doubled the number of Bow labs in by bringing in four new ones. That puts Florida third in the nation, behind Texas (14) and Mississippi (9).

The three federal labs that now do citrus research in Florida illustrate the worth of the farm research pork barrel. In the last 20 years, Florida has doubled its production of oranges and grapefruit from 100 million to 200 million boxes. The Sunshine State now grows citrus fruit on land considered unfit for citrus until research made it fit. Florida has three-fourths of the citrus market in the United States, compared with the two-thirds it had 20 years ago.

No account of the pork-barrel practices of the Senate Appropriations subcommittee would be complete without mention of Sens. Daniel K. Inouye (D-Hawaii) and Mark O. Hatfield (R-Ore.)

Inouye would like Hawaii to become the world leader in tropical agriculture. The Agriculture Department is resisting this effort, mostly because it wants to pursue tropical research in Puerto Rico, which it claims is more truly tropical than the windswept Hawaiian islands.

But don't bet against Inoye. Next month, the 55 members of the Appropriations Committee will vote on a bill introduced by Inouye that would establish the University of Hawaii as a National Center for Tropical Research and grant it $6 million to start its research.Inouye is aware of the pork-barrel aspects of his bill but feels it is justified.

"My motives may be suspect but in the past I have voted for programs benefiting particular states where I consider such programs in the overall national interest," Inouye said. "The same principle applies here."

Then, there's Oregon's Hatfield, who presides over three of Agriculture's laboratories, at Corvallis, Pendleton and Burns. Agriculture wants to close the Burns lab because there is only one scientist working there. The department wants to transfer him to Corvallis, where he would join some 20 colleagues doing watershed research.

Hatfield doesn't want the Burns lab closed and has suggested expanding it to accommodate at least three more scientists to keep its lonesome occupant company. There are people at Agriculture who are betting the Burns lab stays open.