SO NOW IT TURNS OUT that the Pentagon wants to put the new neutron warheads on not only the 56-mile-range Lance nuclear missiles in Europe but on the projectiles fired by hundreds of front-line nuclear artillery pieces as well. What the military friends of the neutron warhead admire so ardently about it is its primary effect of killing people - and killing them in a "clean" way by radiation rather than blast and heat - while inflicting relatively little physical damage on the neighborhood. Thus, the reasoning goes, neutron warheads will be that much more likely to be fired in a crisis and, therefore, that much more effective as a deterrent. Production money for these items is in the Energy Research and Development Agency portion of the public-works bill going through Congress now.

But wait a minute. President Ford, it seems, was at best minimally briefed before he let money for neutron-warhead production slip into the budget stream. No "arms-control impact statement" assessing the effect of the weapon on arms-control efforts has yet been sent to the Hill. Only by a fluke at ERDA, one is told, did that agency reveal it was seeking Lance warhead money; news of the companion request for artillery warhead funds was leaked. Once the word was out, neutron partisans insisted that such quick hearings as could be held take place behind closed doors.

Afterwards, the warhead was approved only by a 10 to 10 committee vote. Says the Pentagon: "no comment." The whole thing has the look of a black-bag job.

The more we hear about the neutron warhead, the less we like it. By making a tactical nuclear response more feasible, it would sap the European allies' incentive to plug the NATO deficit in conventional forces; it would set NATO's nuclear force on more of a hair trigger, when sound strategic doctrine demands a reliable safety catch; and it would commit NATO more deeply to the dangerous premise that a small nuclear exchange can be conducted without serious risk of expanding into a general nuclear war.

From an arms-control perspective, production and deployment of this weapon would fly in the face of the administration's broad effort to persuade other nations to forego nuclear weapons, especially tactical ones. And because of the particular way that "enhanced radiation" warheads kill people, their production and deployment would open the United States to the charge that it was preparing to wage something very much like chemical warfare, a form of warfare that it has formally abandoned.

Mr. Carter, new to the question, promises to make his own decision on it by the fall. But meanwhile, he's allowed the budget request to stand, while he considers whether to withdraw it. Congress could do him - and the country - a favor by knocking the neutro warhead money out of the budget. That would then put the burden of proof of the need for this new weapon where it belongs - on the proponents of the idea - and thereby ease some of the fierce Pentagon pressure on the President. And it would oblige the President, for his part, to make the case to Congress for restoring money for the neutron bomb.