The Soviet Union and the United States today agreed to resume an agricultural exchange program, one of several bilateral agreements that lapsed in 1980 with the collapse of detente between the two superpowers.

The new agricultural agreement, signed today and valid for one year, covers cooperation in research and technology. It marks another step taken by both sides in recent months to restore elements of detente's structural framework.

The agreement commits both countries to exchange specialist teams and information in 20 different fields of agriculture. Visiting U.S. Agriculture Undersecretary Daniel Amstutz said he did not expect the Soviets to provide full information on their own harvests, which have been held secret in recent years. But, he said, the agreement would improve access to Soviet farms.

It also sets in motion a young farmers' exchange program, involving 15 young agricultural specialists from each country who would spend three months on work-study visits.

So far, the resurrection of old agreements and joint commissions has not signaled any tangible warming in U.S.-Soviet relations, which remain undermined by lack of progress in arms control.

Several months ago, when the Geneva arms talks were getting underway, visits by U.S. officals were highlighted here, and contributed to so-called positive "atmospherics" in the U.S.-Soviet relationship.

Since then, the atmospherics have cooled. When U.S. Commerce Secretary Malcolm Baldrige was here recently to resume high-level trade talks after a six-year hiatus, the tone of Soviet remarks reported here was more critical. In the Soviet view, the Baldrige visit did not move U.S.-Soviet trade relations significantly forward.

The handling of today's renewal was another sign that the Soviets are choosing to play down symbolic visits of U.S. officials and the agreements they sign. As of tonight, the accord had not been reported by the Soviet news agency Tass, which yesterday only briefly noted the visit by U.S. Agriculture Department officials.

The agreement was described today by Amstutz as a "rebeginning" of a cooperative arrangement begun in 1973 and suspended in 1980 after the Soviet invasion of Afghanistan.

The agreement is separate from the five-year grain deal, signed in 1981, which commits the Soviet Union to make minimum purchases from the United States each year.