RIVERDALE, CALIF. -- Mark Borba stopped his van on a dirt and gravel track separating two 640-acre sections of farmland in the middle of his domain. On either side tiny new cotton plants stretched for a mile -- dotted lines of green drawn in the rich brown topsoil of California's San Joaquin Valley.

"Our cash out at any one time is enormous," Borba said. "We own all this, but we also own the right to talk to banks and insurance companies about when and how they want their payments." It is, universally, the farmer's lament: Things are almost always bought, but almost never paid for.

Borba, his father, his brother Ross and his boyhood friend, Terry Amaro, farm 12,000 acres of the finest farm property in the United States, a $50 million investment designed to produce an entire menu of crops. This year Borba Farms, Inc. will harvest cotton, tomatoes, sugar beets, wheat, garlic, onions, lima beans, alfalfa hay and alfalfa seed. At last year's prices the cotton alone was worth $5.7 million.

Borba, 39, grandson of Portuguese immigrants, is one of the largest "family farmers" in the country, and his future and the future of others like him will be a likely topic of conversation today when the Senate Committee on Agriculture, Nutrition and Forestry begins what is expected to be a heated debate on farm price supports and crop subsidies. Both houses of Congress are in the throes of drafting the 1990 farm bill, the legislation that will shape the nation's agriculture for the next five years.

Under the 1985 law, farmers are entitled to a variety of federal price supports, subsidies and other benefits designed to stabilize markets and provide help in hard times. Congress predicts these programs under the new farm bill will cost taxpayers $53 billion from 1991 to 1995.

Controversy arises because the government pays farmers based not on what they need, but what they produce. Farmers like the Borbas produce a lot, and there are many like them in the San Joaquin Valley. Fresno County, the heart of this Promised Land, grew $2.6 billion in agricultural products in 1989, making it the richest farm county in the country.

The valley gets a lot of federal money. In fact, a Department of Agriculture document prepared for internal study by Congress in 1989 listed 14 farmers from Fresno and neighboring Tulare County among the richest 50 benefits recipients in the United States. The Borba Family Trust, one of four corporate entities that make up Borba Farms Inc., is ranked 15th in the country, with acreage worth $652,833 in annual federal income supports.

Since 1970, however, the most any farm "person" can receive each year under the program is $50,000. Still, paying $50,000 to entrepreneurs like Mark Borba is not what Willie Nelson has in mind when he sings about aid to the family farmer.

And Borba knows it: "By and large they {the benefits} are aimed at smaller, less efficient, less productive units, and the payment limitation was the first time somebody held up his hand and said, 'Let's call a duck a duck,' " he said. "Farm programs are targeted toward small growers."

But they're not hitting the mark. In 1988 the richest 4.9 percent of farms produced 54.6 percent of farm income, and benefits were skewed accordingly: "Efforts during the past 20 years to make farm programs more equitable appear to have had little or no impact on the distribution of government payments," said a recent Congressional Budget Office study.

Some members of Congress would like to eliminate all payments to farmers earning more than $100,000 a year. Others would like to curb abuses, particularly the "Mississippi Christmas Tree," wherein a farmer spreads his wealth among a dozen family members in hopes that each one will get $50,000.

Borba Farms Inc., near Riverdale some 20 miles south of Fresno, is entitled to four $50,000 payments each year: one to the Borba brothers, one for their father, one for Terry Amaro and one for the Borba Family Trust. Yet even $200,000 is almost insignificant for enterprises like Borba farms:

"You only need 260 acres planted in cotton to get the $50,000," Borba said. "For me, with 5,500 acres, that's 10 bucks an acre. That won't plow the ditches on one cottonfield; that won't apply one coat of fertilizer; it's less than one-tenth of my harvest bill and about one-thirtieth of my fixed annual land cost."

This year subsidies meant so little to the Borbas that they thought seriously about abandoning the program. Being able to ignore government restrictions on how much cotton they could grow was a particularly attractive prospect with cotton selling at more than 80 cents per pound.

They ultimately decided to stay in the program because of what Borba calls "disaster protection." He's not talking about the weather.

"Suppose the government of China suddenly sells all of its cotton," Borba said. "The price drops to 30 cents a pound almost overnight. This is one of those rare circumstances where you need a safety net."

The net is the cotton loan program, which has no limitation and allows growers to cut their losses in hard times by repaying their loans to the U.S. government at a lower rate. The price plunge has happened in the past, and the Borba clan thinks it can happen again.

"Everybody in the world has farm subsidies, and you can lose your shirt to a stroke of the pen," Borba said. "We can't fight someone's foreign ministry, so we need protection."

Borba and most of the other big San Joaquin Valley farmers stand solidly behind the Bush administration's efforts to negotiate freer world markets, so that "we would be able to compete without worrying about politics," Borba said.

Indeed, if big California agriculture bolted the benefit programs en masse -- either because of freer markets or because Congress kicked them out -- the effect on U.S. and world commodity production likely would be profound.

"The government uses the programs in part to control the supply of a particular product," Borba said. "If we leave the programs the government may no longer be able to do that."

Yet this is not a prospect that he finds particularly dismaying, for farming to the Borbas is not home-baked pies, red barns and flapjacks on a chilly morning.

"We've got a $50 million investment here," Borba said. "Are we talking about a way of life, or are we talking about business? Hell, man, that's business."