President Carter, for the second day in a row, sought to turn inflation, one of his most vulnerable points, to his political advantage in a campaign speech to Ohio farmers today.

In praising his administration's farm policy, Carter said a sharp drop in farm prices that he inherited in 1977 has been reversed.

"Corn has gone from $1.60 in 1977 to over $3. Wheat has gone from $2 to over $4. Cattle prices have doubled, from $32 to $64. Milk that sold for less than $10 now sells for over $13," Carter said at Don Schaller's farm outside Toledo.

"I'm not completely satisfied with that record," Carter said in words that could have an ominous ring for food buyers as opposed to food producers. "But, we've made good progress, with more progress to come."

Carter described his address here as "my single major farm speech of the campaign." He attributed the farm programs of the last five decades to Franklin D. Roosevelt's New Deal, and he called the farm policy he inherited from his Republican predecessors "an unholy mess."

Carter said his administration had aided farmers by the farmer-owned grain reserve, which has "taken the government out of the grain business," and by opening new markets, such as China.

The president directly attacked Ronald Reagan for failing to understand "the complex reality of our farm economy." Reagan said early in the campaign that he wasn't familiar with parity, and Carter also quoted him as having said that farm price supports "subsidize the inefficient" and that dairy subsidies "are subsidizing those who could not compete."

Carter also said that "my Republican opponent has tried to make political hay" of the administration's grain export embargo against the Soviet Union. The embargo, imposed after Soviet troops invaded Afghanistan, has been extremely unpopular with farmers, and the president accused Reagan of opposing it solely for political reasons.

"In 1975, he suggested using a grain embargo to force the Soviets out of Angola. In 1979, he threatened a similar grain embargo against Nigeria. Three months before the invasion of Afghanistan, he said, 'If the Russians want to buy wheat from us . . . I would not sell it to them,'" Carter said.

Carter also sought to blunt criticism of the embargo by stressing that farm exports rose $8 billion this year, the biggest single-year gain ever recorded.

Carter's recitation of the increasing prices of bushels of grains and hundredweights of beef came one day after he told a New Jersey audience that the 1 percent jump in the September consumer price index should be taken not as a reminder of failures to control inflation, but of the dangers of putting new inflationary pressures -- such as Reagan's proposed across-the-board tax cut -- on the economy.

In a question-and-answer session before his speech to roughly 1,000 people who crowded the Roy Start High School gymnasium here, the president denounced Reagan's economic proposals as "absolutely ridiculous" in trying to combine a sizable tax cut, a balanced budget and large increases for defense.

"There's no way for him to cut taxes 30 percent the next three years, have a massive increase in the federal spending for defense above and beyond a large increase that's been put into effect by me, without eliminating almost completely all the federal programs that are precious and dear to the people who need help most."

John Drolshagen, an unemployed disabled veteran, asked why veterans are treated as "third-class citizens" and why "the Agent Orange syndrome from Vietnam is being pushed under the carpet."

The president described health problems stemming from contact with the chemical defoliant Agent Orange as "a very serious problem." He said the Veterans Administration is trying "to find out the facts about the Agent Orange effects on people's lives and health." Carter offered no hint of what remedies the government will propose but said he would have Max Cleland, head of the VA, telephone Drolshagen.

The last questioner asked Carter why the president has not run a more positive campaign, emphasizing the greater understanding he can offer as a result of his years in the White House.

"Well, as you know in the heat of a campaign, it's often difficult for a candidate to make those points as well as you just made them," Carter said. The president turned from the question to an attack on Reagan for saying that the U.S. defense is inadequate, then returned to the subject and said it was up to the people to consider such positive issues.

"The point is that the people of this nation in a political campaign have to stop and consider what is our nation's circumstances . . .," Carter said.

The president flew from Toledo to Camp David, Md., for the remainder of the weekend. He will resume campaigning Monday with a rally at Huntington, W. Va., on his way to Cleveland to prepare for his first debate of the campaign, a head-to-head meeting with Reagan.