Lord Soames, Britain's newly installed governor of Rhodesia, today removed an embargo on vital shipments of corn to drought-stricken Zambia in the first major reversal of policy inherited from the defunct Salisbury government of Bishop Abel Muzorewa.

The move came just hours before the Patriotic Front announced in London late tonight that it had accepted British proposals for a cease-fire in the 7-year-old guerrilla war, ending the 14-year-old Rhodesian independence problem.

Soames has been waiting for the overall agreement to announce a series of measures designed to start moving the temporarily recolonized country toward elections of a new government as called for in the London agreement. Until now he has been in a difficult "twilight zone" technically heading a military at war with the Patriotic Front.

It is expected that his first moves will involve lifting the ban on the Patriotic Front political parties and releasing political prisoners.

The agreement sets the stage for Britain to start a major airlift, mainly using American C5A Galaxies and C141 Starlifters, to bring in 1,200 Commonwealth troops to monitor the cease-fire. The airlift is expected to start later this week and continue for five days.

Soames' lifting of the embargo on Zambia today removes Britain from the embarrassing position of being in charge of a government imposing a boycott on a fellow member of the Commonwealth.

There has been considerable grumbling from anti-Muzorewa factions here that Soames had done little since taking office six days ago but meet with members of Muzorewa's former government.

A British spokesman said the lifting of the embargo "is a first step toward normalization of links with neighboring countries." These ties have been strained ever since former prime minister Ian Smith's declared independence from Britain in 1965 to preserve white-minority rule. Soames' arrival last Wednesday formally returned the country to legality.