He flinched a bit when the questions got ticklish, but John R. Block, the Illinois farmer Ronald Reagan wants as agriculture secretary, easily plowed through his Senate confirmation hearing yesterday.

The day-long hearing, about as easy-going as a country picnic, turned up not a single opponent and produced reams of praise for the 45-year-old director of the Illinois agriculture department.

"You have made an impressive appearance. . . . I am proud of you," said Sen. Jesse Helms (R-N.C.), new chariman of the Senate Agriculture Committee. The panel is expected to vote on Block's nomination no later than Jan. 19.

The fireworks that might have been expected over Block's controversial statments on food stamps and food embargoes didn't materialize. Consumer groups, although critical of his food stamp views, did not oppose Block.

Block, in effect, reiterated his disavowals of an earlier assertion that American farm products should be used as a weapon in foreign policy. Rather, he said, food is "a valuable instrument of peace" and embargoes should be "only a last resort . . . under extreme circumstances."

Sen. Walter (Dee) Huddleston (D-Ky.) ranking Democrat on the committee, wondered if Block would consider the Soviet invasion of Afghanistan -- which led to President Carter's ban on certain grain sales -- an extreme case.

"Certainly I don't know all the details and I haven't studied it," Block said.Carter's grain embargo was the source of bitter complaints from farmers who now fervently support Block's nomination.

When Sen. John Melcher (D-Mont.) wanted to know how Block would back up his contention that the food stamp program, now authrized at a level of almost $10 billion, ought to be cut, Block was equally vague.

" I don't have any specific plans," he said. "In North Carolina [alluding to a recent visit there], they were talking about fraud and inefficiency. . . . All USDA programs need to be looked at."

The questioning ranged from that level to the concerns of Sen. Paula Hawkins (R-Fla.), who said she was "overwhelmed" by the number of apparently idle "bodies in the halls and cafeterias" at the Department of Agriculture and wanted to know what Block would do to promote Florida citrus sales in Japan.

Block, who raised soybeans and hogs on 3,000 acres in northwestern Illinois, said he would be a tough bargainer with the Japanese but could make no promises on eliminating bodies at USDA.

Sen. David Pryor (D-Ark.) wondered what would be different between a Block administration at USDA and that of the incumbent secretary, Bob Bergland. Not all that much, seemed to be the answer.

"I think it will differ in tone and philosophy and in direction . . . our philosophies are somewhat different," Block said, without being more specific.

But clearly, farm-oriented members of the committee, the farm groups that praised him and Block himself, through comments yesterday, see the secretary-designate principally as a drum-beater for American farmers.

Helms and others on the committee, chiefly Roger Jepsen (R-Iowa) and Mark Andrews (R-N.D.), urged Block to get out the message about farmers' needs and their generally high levels of productivity.

Block stressed repeatedly that he would push policies aimed at broadening American farm markets overseas, while assuring "profitability" in farming and generally protecting consumer interests.

"What do you tell consumers who fear that exports lead to higher prices at home?" asked Jepsen.

"That is very shortsighted," Block said. "Exports are to the benefit of the country. Exports provide a stronger agricultural industry, jobs in every town, a climate for more efficient agriculture. It is in the long-range interests of everyone to have a strong export program."

The secretary-designate also said he would put emphasis on more agricultural research, on helping developing nations become agriculturally independent and on using U.S. farm products for alcohol-fuel production.

"I will be a strong voice and a strong advocate for agriculture," Block said. "I can stand on my own and hold my own in the halls of government."

Helms and Huddleston indicated Block will be confirmed without difficulty but the committee still must review his financial disclosure statements, which Block said yesterday would reveal a debt of between $3 million and $5 million on his farm properties.