GILL, MASS. -- The black and white Holstein cows maunder lazily about the hillside pasture that Charlene and Mike Berniche carved from the woods and the new barn sparkles under a bright fall sun, but the serenity deceives.

In less than a decade, Charlene Berniche, a dairy farmer, and her husband have gone from scratch to farming success. Their cows are super producers, and every drop of their milk is sold in New England, which consumes more than the region's farmers can turn out.

Because of high demand and tight supplies, dairy farmers in the Northeast receive more for their milk than the federal support that sets a floor under prices nationally. It is a seller's market; life on this farm should be copacetic.

But theories go askew here. Like other Northeast farmers, the Berniches are about to be jolted by a national price reduction that will further trim the margins in an operation that rewards them only minimally for dawn-to-dusk toil.

Why a cut in the support price, when there's not enough milk to go around in New England?

Under the program adopted by Congress in 1985, dairy supports must be cut when government surplus purchases reach 5 billion pounds per year, and that is expected to occur in 1988. Thus, farmers such as the Berniches who produce no surplus are penalized for the excesses of farmers elsewhere who turn out more milk than they can sell.

"The price cut they're talking about would cost us $5,000," Charlene Berniche said. "Our farming expenses do not go down. The reduction will hit our personal living expenses. We'll have to make do with less, and we don't pay ourselves $100 a week as it is. A high school kid at McDonald's gets $5.50 an hour around here."

Agriculture Department statistics help pinpoint the problem:

In the fiscal year that ended Sept. 30, the government bought 5.6 billion pounds of dairy surplus. But only 2.6 percent of that came from the East region, which includes the southeastern states. The bulk, 56.5 percent, came from the Midwest, and 40.9 percent was from the West, where production is climbing steadily.

With federal purchases expected to exceed 5 billion pounds next year, dairy farmers are girding for a support reduction of 50 cents per hundredweight of milk in January. The cut will affect all farmers, whether they produce surplus or not, and it is likely to be fatal for many already on economic thin ice.

This prospect has set off a new debate in Washington, where dairy farmers from areas that contribute little to the surplus are pushing for radical changes in the dairy program.

"We have a regionally biased dairy policy for surplus areas. It has let them shift the cost of the program to the Berniches and other dairy farmers in the Northeast," said Steve Kerr of Westminster, Vt., a former congressional dairy adviser who now heads the Legislative Conference of Northeast Cooperatives.

"It is unfair," he continued. "If the surplus problem is in California and you don't put the production disincentives there, then it is unfair. Dairy policy over the last five years has ignored that. And farmers are upset because they have had to bail out other areas. The program is exactly backward. If we start making too much milk, we ought to have to pay for it."

The theory behind the program is that, as the government's guaranteed price goes down, farmers' profit margins will narrow and they will curb production. And as farmers react, the theory continues, government surplus-purchase costs will go down. In fact, however, many farmers respond by producing more to keep their income up.

"At what point do we give up? We'll just milk more cows," Charlene Berniche said. "I don't see why we in the Northeast have to pay the bills for everybody else. Why don't they assess just the surplus areas? We pay off our bills, and now we're going to have to pay for others, too."

Her complaint is heard throughout New England, where the dairy industry is pressed by high operating costs. Fresh milk supplies have dropped in the last two years because of another facet of the federal surplus-cutting program that enticed farmers into retirement.

The New England states, which require milk from other regions, lost 10 percent of their dairy farmers in the "whole-herd buyout," a part of the 1985 farm program that attacked the chronic surplus by paying farmers to quit. Ignoring regional supply imbalances, the buyout was open to farmers everywhere.

By the time it was completed this fall, the $1.8 billion buyout, financed in part by farmers, reduced the dairy herd to its smallest size in 120 years by removing 1.5 million cows from production. But as milk output also declined, farmers readied more young heifers to go back to work once the program ended. As a result, production is expected to soar again.

The other cloud hanging over New England's dairy supply outlook is urban-development pressure, luring dairy farmers into retirement with offers of big money for their land.

The situation is considered so alarming that the Massachusetts state government, for one, is working to try to keep farmers on their farms. Its efforts include a farm land preservation plan and a new program to help farmers cut costs and boost income by composting manure and other wastes.

"Dairy farms in New England are developers' dreams," said August (Gus) Schumacher Jr., Massachusetts commissioner of food and agriculture. "Dairying is the Northeast, although we only produce 15 percent of our total {milk} needs in this state. We are down to only 545 dairy farmers after losing about 100 in the last 18 months, due to the whole-herd buyout, economics, retirements and developmental pressures."

Reacting to the complaints from dairy farmers at home, Senate Agriculture Committee Chairman Patrick J. Leahy (D-Vt.) and other northeastern lawmakers are proposing legislation aimed at regionalizing the federal dairy program. Price supports would be cut in overproduction areas.

"We work under a system which assumes that everybody is treated equally," said Ron Allbee, Vermont's agriculture commissioner. "But a majority of the excess production comes from the West Coast, which lets them take advantage of the federal system."

The Leahy approach, being backed in the House by Rep. James M. Jeffords (R-Vt.), would leave the price-support system intact. But it would divide the country and require farmers in each region to keep production in line with demand to avoid the surpluses that would trigger further price cuts.

Leahy and Jeffords said in interviews that, unless national policy is changed by allowing farmers in lower-producing areas to avoid the shocks of price cuts, regional economies and regional stability will be disrupted.

"We need the stability that comes from agricultural diversity . . . . we can regionalize this program, or we will see parts of this country with no dairy farmers," Leahy said.

"In Vermont, we would long regret that. Agriculture keeps land open, and the rural stability has attracted high-tech interests. But we are small, and we get whipsawed by economic trends. We now have to maintain the diversity in agriculture, in an atmosphere where it can be viable," he said.

But, Jeffords noted, their regional idea will be difficult to achieve politically, with dairy farmers divided and legislators from surplus areas not keen to impose costs on their constituents when farmers elsewhere share the burden.

"It is hard to say what will happen," Jeffords said, "but the bottom line is whether the dairy industry wants the price support system or not. If we do not change the program, they won't have the system."

A final word came from Raymond Duda of Easthampton, who with 400 cows is one of this state's largest dairy farmers. He also is the Reagan administration's state director of the federal Agricultural Stabilization and Conservation Service, which oversees farm programs here.

"We have the biggest markets in the country but others can come into our markets at lower production costs," Duda said. "In the Northeast, we cannot expand -- the land's not here. We have been surviving through our efficiency and technology, but how much more efficient can we get?

"We are going to have to decide if we want small people to produce our milk or whether we want it done by just one big dairy farm."