The Chinese lesson

China is once again buying US wheat, cotton, and soybeans, thanks to a new bilateral textile accord which promises increased US purchases of Chinese textiles.

What does the textile pact have to do with wheat sales? Farmers are only now beginning to understand the close ties that bind US export- and import-competing industries.

It has been a very costly lesson.

During the past year the United States tried to tighten limits on Chinese penetration of the US textile and apparel market. In response the Chinese sharply cut back on imports of US farm products, which last year totaled about $ 1.5 billion. In the first half of 1983, Chinese imports of US wheat dropped from to $1.1 million; and imports of soybeans went to zero.

Buy our goods, the Chinese said, or we won't buy yours.

What is startling is not that the Chinese retaliated against threatened new US import restrictions, but that such actions have not been resorted to more often. To be sure, the risk of retaliation by our trading partners has been often cited by free-trade advocates as an important argument against new trade barriers. Yet such action has seldom been taken in the postwar period. Over the years, countries have been loath to retaliate against the US, for fear of endangering a trading relationship which was more important to them than it was to us.

Without the fear of foreign retaliation, Congress has spawned a number of protectionist bills that have been used to coerce our trading partners into restrictive market-sharing agreements, which limit US imports through ''voluntary'' restraints by foreign companies. This is born-again mercantilism: making auto, steel, and textile industries better off by hurting our trading partners.

The US has not had to consider the consequence of such measures because no country has tried a similar approach.

The tide may be turning, however.

In response to new protectionist measures for the US specialty steel industry , the European Community has asked for compensation - as is its right under world trading rules - for the damage done to its traders. Concessions are also being sought in the form of lower US duties on EC exports of products such as carbon steel, machine tools, and whiskey.

If concessions are granted, it will mean that certain US industries will pay (in the form of increased foreign competition) for the protection given to the specialty steelmakers. If no agreement is reached, the EC has threatened to retaliate by limiting key US exports to Europe. In that case, it would be US exporters who would be at risk. One need not be overly cynical to assume that the EC is giving the US some of its own medicine - threatening draconian import curbs unless the US agrees to limit ''voluntarily'' exports of such products as soybeans and corn gluten. In short, US farmers are liable to be called on again to pick up the tab for US import restrictions.

The cost of protectionism may well be lost exports and jobs.

The Chinese have taught a valuable lesson: Trade is a two-way street. If the US wants to export, it needs to import as well. US trade officials would do well to consider who bears the burden of its trade policies before embarking on protectionist ventures.