BY LOOSENING the accounting rules for banks that lend to farmers, the federal bank regulators are taking half a step in exactly the wrong direction. They are doing it reluctantly, to deflect Congress from much more drastic action in the same wrong direction. But it's unpleasantly reminiscent of the route by which the savings and loan industry fell into its present troubles.

With the surge in interest rates at the beginning of this decade, the S&Ls began suffering heavy losses. The federal S&L regulators anxiously responded by loosening the accounting requirements under which those losses are handled. The result is that there is now a large number of federally insured S&Ls -- 461 of them, at the middle of last year -- that are still open and taking deposits, but are in fact insolvent by the generally accepted accounting standards that prevail elsewhere in the business world. Since their stockholders have been wiped out, their managers have nothing to lose by taking plunges on highly risky investments to try to recoup. That has compounded the losses, and the regulators now cannot afford to close down the 461 insolvent institutions because there isn't enough money in the federal S&L deposit insurance fund to cover their liabilities.

Now the banks seem to be about to repeat the unhappy pattern. Last week the three federal regulators -- the Federal Reserve, the Federal Deposit Insurance Corporation, and the Office of the Comptroller of the Currency -- uneasily agreed to bend some of the requirements for the banks heavily engaged in lending to farmers. A bank "experiencing difficulties" will be allowed to operate with less than the normally required capital for a period up to five years.

Earlier this month both the Senate majority leader, Robert Dole, and the chairman of the Senate Banking Committee, Jake Garn, promised rapid action on legislation that would do the same thing and more. Unfortunately, the distress of these banks is real. Most of them are small, and most lack other markets to which to turn. Many farm banks are also lenders to oil producers, and the effects of the farmers' losses are compounded by the falling price of oil. Relaxing the requirements for the farm banks establishes a precedent for doing the same thing for the oil banks, and then for the banks that are having trouble with their real estate loans.

Is it really a smart idea to reduce the capital requirements for a banking system already under great strain? Is there nothing to be learned from the experience of the S&Ls?