The grain embargo is on the way to being dumped by competition for the farm vote and Soviet success in buying abroad. But what of the other major part of the Afghanistan-induced ostracism -- science or technology?

The customany clean-slate mood of the post-election period will provide a good time to think about that, because persuasive, though politically sensitive, arguments are being raised that the science-related cutoff is both unproductive and perilous.

There's no simple scorekeeping on the effects of the government-decreed and voluntary cutbacks in American contacts with Soviet researchers and in commercial sales of high-technology equipment. What's obvious is that, even if the reductions are interfering with Soviet scientific and industrial timetables, the Soviets remain in Afghanistan and persist in abusing their dissidents, including the neverated Andrei D. Sakharov.

The Soviets obviously once put a high value on access to American scientific know-how and goods, as was evident in long ago Cold War days, when they set aside xenophobic tradition and let in some of our specialists as the price for their own coming here. But, given their national pride, substantial industrial and research, base and record for getting along on their own when necessary, it's not jarring to find them bristling and unresponsive to efforts to link science cooperation to foreign prescriptions of good political behavior.

We can't be certain what the cutoff is costing them, but it's probably less than many boycotters have hoped for. The Soviets never permitted themselves to become heavily dependent on American scientific and technological prowess. To the extent, however, that they once found advantages in tuning in to advanced work here, they now find many comparable opportunities in Western Europe's booming research enterprises, where the boycott fervor is relatively underdeveloped. As for advanced equipment, there are indeed some items, particularly big computers, unique to American producers, but not many. And, regardless of Western agreements barring sales of supposedly sensitive equipment, Europe's normal East-West commercial traffic is so heavy that it's impossible to track all forbidden goods.

If all that could be said against the boycott is that it's scientifically and diplomatically unproductive, it might still be argued that the boycott is heartening for the dissidents and good for the moral fiber of its participants.

A dissenting view, however, is gaining strength in the scientific community, and recently was brought into the open in an editorial in Science magazine by William D. Carey, executive officer of the American Association for the Advancement of Science, which publishes that widely circulated and influential journal.

The boycott, he wrote, merits re-examination not only because it hasn't worked but, more important, because it has interrupted a channel of reasonable dialogue between influential scientific leaders in both nations.

"It violates no confidences to report that leaders in science in both countries view the present tension with undisguised alarm," Carey wrote, adding that "we are very nearly out of safety valves as the nuclear superpowers drift toward impasse. . . . The quarantining of Soviet science," he continued, "however principled, defeats the chances for engaging a concerned and far from impotent cohort of opinion and influence in a dialogue of reason."

The independence and political influence of the Soviet scientific elite is another imponderable in the affairs of the two countries. But given the darkness that is settling in on Soviet-American relations, some benefit of the doubt might be granted the contention that the scientific elite includes some of the least dogmatic and most cooperative-minded leaders in the Soviet hierarchy. Also, with high-level leadership changes imminent there, the good -- but now blocked -- personal relations that American scientific leaders once enjoyed with their Soviet counterparts could be a valuable route of communications.

The nuclear standoff has endured for so long that its fragility is often overlooked. In this regard, it's useful to keep in mind recent warnings by Dr. Howard Hiatt, dean of the Harvard School of Public Health, who has embarked on a campaign to dispel foolish notions about the medical system's being able to do anything useful after a nuclear attack. Doctors, nurses and hospitals, along with everything else, will be obliterated, he warns, adding that "nuclear war isn't unthinkable. It just hasn't been thought about."