DISTRESS AMONG American farmers this winter is real and widespread. But the kind of assistance over which the Democratic senators and the Reagan administration have been quarreling can make only a modest contribution. It will provide slightly easier credit to farmers who already have too much debt. It suffers from the same illusion as many of the farmers -- that their troubles are only temporary, and can be resolved by one good season. This kind of asistance is worth giving, but only for the modest reason that it provides, in a small way, a shock absorber. It can reduce, at least in a limited way, the impact of farm failures on the communities in which they are likely to be concentrated.

Farmers are the victims of their own astonishing productivity. It's not the farms that are disappearing. The number of acres under cultivation in this country has not changed much in half a century. But farmers' productivity -- the amount that they can produce per hour worked -- is now seven times higher than it was in 1950. That rise in productivity, and not any shortage of credit, is the basic reason why farmers have been leaving the land. The government can't interrupt that process. It can only slow it down a little, in the hope of limiting the social damage in the bad years.

The farm economy moves in cycles in which the troughs are painful, even with protections like minimum price supports. The Reagan administration now proposes to abandon stable price supports and replace them with flexible minimum prices that will fall over the years if market prices fall. Congress has to enact a comprehensive farm bill this year, and this concept of flexible minimum prices will be at the center of the debate. The administration wants not only to save money but, it argues, to expand American farm exports by allowing prices here to follow world markets. The idea is fundamentally flawed.

It is quite wrong to suggest, as President Reagan did last week in his press conference, that wider access to export markets will be the salvation of American farmers. The export markets are much less predictable than domestic demand. It was the wave of foreign demand for grain in the early 1970s that started the chain of events -- temporarily high prices leading to inflated land values, followed by falling exports and unmanageable farm debts -- from which many thousands of farmers are suffering now.

The government's first responsibility in agriculture is to maintain efficient and reliable production of the country's food supply, at prices that do not jump wildly and disruptively from one season to the next. That can't be accomplished without greater government intervention than the administration wants to devote to it. Exports are an important part of the farm economy -- but they are the least stable part of it.