MOST YEARS farm-state members of Congress with seats on the agriculture committees regard themselves as fortunate. This year they can be forgiven if they do not. The committees are writing a new farm bill to restructure the costly and complex support programs that expire Sept. 30. It is the worst of all possible times to have to do this: support costs are high in a tight- budget era, and farm income is low. To help U.S. products move in world markets and to stay within the budget, the committees have to reduce price and income support levels. They know it, but don't want to do it; they have been looking wishfully for alternatives ever since Congress convened six months ago. Now they are up against not just vast surpluses and low world prices, but the clock.

The Senate committee has promised Majority Leader Bob Dole, a senior committee member from a wheat state, that it will have a bill ready for floor action in another week. Congress is scheduled to be on vacation all of August, and September is planting time for the winter wheat crop, the first crop the new bill would cover. "It's pretty hard to go home in August and not have a wheat bill," Mr. Dole observed. But straw votes on the support issue before the July 4 recess were inconclusive. A test vote on the administration's idea of moving price supports below prevailing market prices, so farmers would sell to the market instead of the government, ended in an 8-8 tie. Members didn't want to commit themselves on price supports until some decision was reached on the separate program under which farmers are also given government checks in low-price years as income supports.

The committee also considered alternative proposals under which farmers could vote in referendums to limit production. Lower production presumably would mean higher market prices, and save the legislators from having to vote for lower price supports. But "supply management" programs are complicated if not cumbersome, and the committee voted them down.

On the House side, members were so torn that instead of reporting out no alternative, the grain subcommittee reported out three, which at least in principle conflict. One is a supply management bill and one a new crop loan system that could add to costs rather than cut them. The third, offered by subcommittee Chairman Thomas S. Foley, House Democratic whip, is the straightforward one. It would lower support levels but -- in deference to the distress in the farm states -- not as fast as the administration has proposed.

The budget resolution also requires that the committee let down income supports, though this too should be done gently. There is no fun in this; the agriculture committee members have the year's dirtiest job in Congress. But farmers also know the support programs cannot be sustained in their present form. The best politics, no less than the best economics, may be to do it right, and get it over with.