There are, I suppose, other things besides grain which the United States could withhold from the Soviets to their disadvantage; although offhand I cannot think of any others except in the area of high technology which is supposedly policed anyway.
One of the difficulties about trying to put pressure on Moscow by withholding something is that the Soviet Union is the most nearly self-sufficient of any country in the world. It lacks only two raw materials within its own borders - natural rubber and quinine. Otherwise, it has all the metals, all the foods, fibers, and wildlife that matter in commerce and trade.
The US is short of more things useful to modern industry. Chrome is one. If it came to a battle of boycotts, the Soviets could deprive the Americans of more than the Americans could deprive the Soviets.
Except for one thing - grain.
It is merely one of the curious things about communism as it works in the Soviet Union that it cannot manage to make the good earth produce good crops.
The Russia of the czars was self-sufficient in foodstuffs.
The Ukraine has long been one of the world's most generous producers of grain. It was a rich land in the days before the communist revolution. Stalin deliberately starved the peasants of the Ukraine to bring them to heel. Somewhere between 2 million and 6 million (there is no provable count) Ukrainians died of starvation in that induced famine. The Ukraine retaliated by not producing for the communists what it once did for the kulaks.
Today, because of inefficiencies and poor weather conditions, the Soviet Union is chronically short of grain. Without the coarse grains it becomes short of meat - which Soviets seem to want quite as much as other peoples do. Without the fine grains they might run short of bread.
The US has the world's highest capacity to sell or withhold grain. The ability to withhold is the strongest form of economic leverage which the US has over the Soviet government and its policies. Others - Argentina, Australia, France, Canada - can supply grain. But not all of them together can comfortably supply the quantities which the Soviets want.
Besides, if the others were to take over entirely the supply of grain to the Soviets, those others would probably have to buy from the US to fill out their own needs. The US is both the world's largest granary and the granary of last resort.
Which makes it all the more surprising that at a time when President Reagan holds the Soviets responsible for the suppression of Solidarity and hence of political freedom in Poland, and applies economic sanctions on Poland for that deed - he turns around six days later and offers to sell the Soviets more grain than they have ever before imported from the US, and more than they could probably handle even if they wanted it from the US. He even promises that if they order 23 million tons during November he will guarantee its delivery for six months - no embargoes.
All of which reverses the normal role in such matters.
The US President is begging the Soviets to buy a huge quantity of US grain. By doing so, and by the manner of his remarks in the doing, he is advertising the dependence of the US on the Soviet grain market. He wants to sell them more than they need or probably wish to buy from the US.
Thus President Reagan has thrown away the strongest and best piece of bargaining leverage he has over the Soviets. Some experts think it is the only real leverage he has. Besides, his obvious desire to sell them the grain actually gives them leverage. They can say, ''Well, what favors will you do for us if we agree to take those 23 million tons of your surplus grain off your hands?''
He wants to sell, more than they want to buy.
Which means something in other areas because there is ''linkage'' in all international transactions and two can play at the linkage game.
From now on every time American diplomats meet Soviet diplomats over some negotiation there will be in the back of the minds of the members of the Soviet delegation that Mr. Reagan needs their market for his grain, and is eager to sell them grain in spite of all the unkind things he has previously said about them.
Besides, Mr. Reagan cannot be very serious about waging an economic ''cold war'' against the Soviets if he is willing to throw away his best piece of leverage against them.
The only reasonable and plausible assumption which any diplomat can draw from the affair is that President Reagan's anti-Soviet talk is just talk and that he is a cold warrior against the Soviets on the American political hustings - but not in the real power world.