The farmer from Indiana was a little intimidated by the big hearing room and the importance of the subject--how to deal with the faltering farm economy--but he went ahead and spoke his mind.

"It's kind of hard to speak to empty chairs," Robert Leader of Brookston said to the four members of the 43-man House Agriculture Committee who remained for the hearing.

His friend, Martin J. Hoffman of Hebron, Ind., added: "If I have a sinking heart, it's because of that....We spent our own money to come here. It makes me go home sad that we don't have someone here to hear about our plan. It saddens me."

"Don't feel badly. Your trip has not been in vain," said Chairman E (Kika) de la Garza (D-Tex.), as he apologized for his 39 absentees. Some had been around earlier as the committee began hearings on a "farm-crisis" bill designed to deal with the current economic pressures on agriculture.

The bill, proposed by more than three dozen Democrats and Republicans, would pay farmers to retire additional production acreage and would call a national referendum on retiring cropland in return for higher federal price supports.

The idea is to reduce production, draw down huge supplies of basic grains and increase prices. According to the Congressional Budget Office, the bill would reduce government farm spending by about $900 million over four years because of lower direct subsidy payments to farmers and storage costs.

But the Reagan administration, which pushed hard for the 1981 farm law that the legislators are now trying to rewrite, is expected to oppose the bill, partly because it wants Agriculture Secretary John R. Block to retain flexibility in dealing with production and subsidy problems. Testimony by Block, who was expected to announce his opposition, was postponed until early next month because of the congressional budget debate.

Except for the American Farm Bureau Federation, which is on record against the bill, the farm organizations appearing yesterday registered varying degrees of support for the measure engineered by Reps. Tom Daschle (D-S.D.) and Kent Hance (D-Tex.).

Marvin Meek, chairman of the American Agriculture Movement, called the bill "a step in the right direction," saying that farmers are demanding action and leadership from Congress. He urged the committee to ignore the objections of more traditional agriculture groups.

He contended that grain companies, cotton shippers and the Farm Bureau do not represent grass-roots farm views. "They treat Congress like a mushroom--they keep you in the dark and feed you horse manure....It's high time we find out what farmers think."

The National Farmers Organization; Midcontinent Farmers, a farm cooperative based in Columbia, Mo., and cotton and grain farmers from the lower Rio Grande valley also supported the pending bill. They warned that, without assistance from Congress, farmers will face massive foreclosures and failures this year.

But none of their suggested amendments, or the bill under consideration, is as simple as the plan of Hoffman and his friends from Indiana. They propose that farmers vote on a plan to retire 15 percent of U.S. cropland acreage while the government acquires a grain reserve to cover consumer demands.

Farmer Gibson Gray of Fairland, Ind., told the committee that a land-retirement program would be the quickest and most efficient way to force a change in commodity prices. "Your crisis bill will not be as effective as you hope," he said. "The alternative is a sure thing."

Prices automatically would begin moving up, said Hoffman, and "farmers would have the chance to correct their own problems." How would farmers vote? Of 500 Kentucky farmers who voted in March, he said, 81 percent favored it.