AGRICULTURE SECRETARIES come and go. Jamie Whitten stays, and as chairman of the House Appropriations subcommittee on agriculture, has often seemed to run the department. The process continues; his latest target is the conservation reserve that Congress established in last year's farm bill. The reserve is an effort to make up for the excesses of the 1970s, when farmers were encouraged, partly by government policies, to expand production, particularly for export. In the process they moved onto erodible land; an eighth of the land now in cultivation across the country is said to be highly erodible. It is farmed at enormous environmental cost.

The reserve program would pay farmers to retire this land, which is good conservation policy. In a time of overproduction, weak prices and burdensome support costs, it is good farm policy as well. But Mr. Whitten seems not to like it. He is said on the one hand to fear that the country will idle so much land it will forfeit export markets. Closer to home, the authors of the reserve program provided that in its first two years it would not be subject to Mr. Whitten's appropriations process; its funds would be assured. They justified the favored treatment partly on grounds that the cost was uncertain, so that Congress would not know in the early years how much to appropriate, while farmers might not sign up if funding were in doubt. What they really feared was that in tight budget years a large new conservation program might not survive.

The Appropriations Committee has always resisted such swipes at its jurisdiction -- and this time the turf issue had extra frost on it. Mr. Whitten has been a special patron over the years of the department's much smaller traditional conservation programs. While the new conservation program was to have its start outside his cotrol, the administration was proposing that these older programs be cancelled out.

He first proposed to take away the favored status of the conservation reserve and route funds through the appropriations panel. That failed. He is now proposing, as part of a supplemental appropriations bill scheduled to come up next month, to limit the extent to which any one farmer can participate in the reserve. He says he wants to keep the program from being abused. Conservation groups and members of the Agriculture Committee say he is using the appropriations power to block the will of Congress and ought to give the reserve program a chance. Mr. Whitten, because he is also now chairman of the full Appropriations Committee, is not easily trifled with. But on this issue an effort will be made to beat him. Someday there may be good reason to amend this program, but not now. Farmers are already signing up; the House should keep it as it is.