U.S. policies toward Latin American debtor nations have seriously hurt American farmers and manufacturers without doing much to resolve the debt crisis itself, according to a congressional Joint Economic Committee study released yesterday.

The only beneficiaries of the administration's approach to the debtors have been banks and bank shareholders, the study said. The banks have continued to receive interest payments from nearly all the debtor nations, and profits and bank stock prices have risen in the last four years.

Even the initiative announced by Treasury Secretary James A. Baker III last October does not differ "significantly from existing policy," the study said. The so-called Baker Plan does little more than change "the rhetoric to growth from austerity" and shift overall management of the debt crisis from the International Monetary Fund to the World Bank, the study said.

The increased funds that Baker proposes to funnel to the debtor nations still will go to pay interest rather than stimulating growth and investment, it noted.

The study said that the banks had to be protected to prevent a massive credit crunch and sharp upward pressure on interest rates. "But the decision to intervene and avert a financial collapse was only a first step. The second step should have been to consider -- and minimize -- the impact of the debt crisis on the U.S. economy," the study said.

The study said banks should have been required to slowly write off forgive some of their Latin American loans, while limiting the amount of interest they required from the debtor nations.

Such a policy would have helped U.S. exporters, who lost many of their Latin American markets because the debtor nations cut back foreign purchases, and the debtors themselves, who had to neglect domestic investment and the food needs of their citizens to pay foreign interest.

The policy also would have slowly reduced the size of the debt, alleviating the threat it poses to the world financial system, the study said. As it is, nearly four years after the crisis began, the massive Latin debt still hangs over the world financial system, the study added.

Such a policy would have slowed the growth of bank profits, but "would not have represented a serious blow to bank profitability," the study concluded. Commercial banks around the world account for about two-thirds of Latin America's $370 billion in foreign debt.

The study said, "The Reagan administration's management of the debt crisis has, in effect, rewarded the institutions that played a major role in precipitating the crisis and penalized those sectors of the U.S. econmy that played no role in causing the debt crisis."

In broadest terms, debtor nations were required to undertake financial austerity programs to conserve dollars -- by trimming government spending and cutting back imports -- and to step up their exports to earn more dollars.

In return for the austerity measures, the countries received loans from the IMF and from their commercial bank lenders.

As a result of the measures, the debtor nations cut back their purchases from the United States.

"Nearly 50 percent of the trade surplus that Latin America needed to pay interest was generated by reducing its purchases of U.S. products," the study said.

In 1981, Latin American nations purchased $6.9 billion worth of U.S. farm products. Last year, they bought $4.5 billion.

Not only did debtor nations sharply cut their purchases from the United States, they stepped up their production of many products to earn the dollars they need to service their debts. That drove down prices worldwide for farm products and other products from copper to tin. Latin American exporters also took away export markets from U.S. producers.