THE FARMERS' protest movement is now in tis third month, and the time for spring planting is getting close. Over the winter, these farmers have succeeded in gaining the attention of their customers in the cities and evoking a good deal of sympathy. They won't get the remedy that they have been demanding. Parity is an obsolete formula that would guarantee wildly high farm incomes, nearly doubling the present prices of wheat and corn. But there are other ways, less drastic and less disruptive, to help the farmers who are in trouble.

The farmers who are in trouble are by no means all of the country's farmers, or even a majority. There's a clear pattern to the distress. Keep in mind that there was a severe shortage after the 1972 grain-crop failures in many parts of the world, but especially in the Soviet Union. When the bidding for scarce supplies sent the grain prices up, the price of farm land followed. The more valuable the crop, the more valuable the land that produces it. But in the past couple of years there have been huge harvests, in this country and around the world. When grain prices came down, land prices stayed high.

The farmers who are in trouble now include a lot of operators who bought land at the peak of the upswing, from 1973 through early 1976, and are now trying to make mortgage payments in a time of relatively low prices for their crops. The people who rent land are also in trouble, because rents reflect land values. So are those who invested heavily in expensive farm machinery, anticipating revenues that never arrived. As you would expect, these farmers are dsproportionately young men, just getting started in business. Older farmers who bought their land before 1973 have enjoyed enormous capital gains on their land investments. That is the explanation for the statistical paradox of a steadily rising total of farm wealth, accompanied by genuine distress on the part of some farmers.

Some of the current stress has local causes. There are farmers who were severely hurt by last year's spotty drought. Some farmers' costs are rising much faster than others'. For example, there are farmers in Texas who grow wheat on land irrigated from deep wells into sinking water tables; the pumps are driven by natural gas. Their costs bear no resemblance to the much more moderate increases in other wheat areas farther north.

Large increases in basic grain prices, mandated by law, could only do grave harm. Beyond the inflationary effects, and beyond the damage to exports, they would incite another round of rises in land values. The process in circular: Higher price supports are immediately capitalized in increased land prices, setting still higher hazards to people entering farming and buying or renting land. The magnitude of these increases, incidentally, is not small. The value of farm land in Iowa has more than tripled over the past five years.

The administration hopes to coax grain prices up a little, gradually, over the summer. For the first time since 1973, it is offering to pay farmers to set aside land. It is also encouraging a modest program of building government-supported reserves on the farms. According to this strategy, the reserves will take off the market the unusually large surpluses from the past two bumper crops, and the set-asides will restrain the 1978 harvest. To carry through those farmers who are now overinvested and desperately short of cash, the Agriculture Department is providing emergency credit, and the House Agriculture Committee is at work on legislation to expand that credit. It won't make the protesting farmers rich, or even secure. But it will save most of them from disaster.

Why save farmers? Because we need them. Because, to borrow a noble line, bread is the staff of life. Because they are in a business where the risks are uncontrollable. Speaking of uncontrollable risks, it is useful to keep in mind that federal policy will only modestly affect grain prices over the coming year. The greatest influence over prices next autumn will be the rainfall in places like India, Argentina, the Soviet Union and Kansas.