THE HOUSE Agriculture Committee is doing a generally good job of cleaning up after itself. Its subcommittees decided that some other sector of society should reduce the budget deficit -- this is, after all, an election year -- and pretended to approve large increases in price and income supports in the farm bill Congress is writing this year. Now most of the increases have been or are in the process of being rescinded and the support programs put at least in the fiscal equivalent of neutral. The egregious exception is in the dairy program. The way the panel has provisionally voted, you would think it was cows that oinked.

The dairy section was one of the best in the expiring 1985 farm bill. What made it so was that it based supports on likely production. If the going support price seemed likely in the judgment of the agriculture secretary to elicit too much production in the year ahead, the bill provided that it be automatically reduced. Similarly, if it seemed likely to elicit too little production, it was to be increased. Supply and cost to the taxpayers were both controlled.

The dairy subcommittee's original idea was to drop this useful mechanism, increase supports and then go through a lot of convoluted steps to minimize or mask the cost. When that wouldn't wash, the members came up with a compromise that they were pleased to call a support price freeze -- like the freezes toward which the committee seems to be tending for other products. The dairy freeze turned out to be a half-freeze only. The old mechanism would be preserved, but it could only adjust prices up, not down. If too much milk was then produced, the department would be empowered in other ways to manage supply.

The chairman of the dairy subcommittee is Rep. Charles Stenholm of Texas, the ranking minority member, Rep. Steve Gunderson of Wisconsin. In other contexts -- which is to say, when less favored programs are on the floor -- Mr. Stenholm yields to none in championing economy. Here he seems to have lost his voice. Estimates are that the compromise he favors would add as much as a billion and a half dollars to the five-year cost of the bill.

There are problems with the current dairy programs, but they are mainly distributional -- some producing regions and some milk byproducts are favored at the expense of others. But these can be dealt with without destroying the underlying mechanism, which is rational. Congress should vote to preserve it. So should the agriculture committee before it sends this bill to the floor.