Nicaragua's new revolutionary junta announced tonight that state-owned export companies will market the country's agricultural production abroad.

Sergio Ramirez, a member of the junta, said Nicaragua's principal agricultural exports - cotton, coffee and sugar - are too important to the country's economic well-being to leave their sale in private hands. In a normal year, Nicaragua earns about $600 million from the sale of its agricultural produce.

The decision to nationalize the important agricultural sector came about two weeks after the junta announced, in one of its first acts, that it had nationalized the country's banking system.

Foreign banks still will be allowed to operate here under certain limitations, but observers said tonight that their future profitability in Nicaragua could be affected severely by the junta's decision to take control of the export, and possibly the financing, of agricultural production and sales.

In another decision announced tonight, the junta said that it had begun a series of municipal "elections" - which will use a system that probably would be considered undemocratic by Western standards.

Junta member Moises Hassan described an election that took place today in Leon as a model for other cities throughout the country. Hassan said that the Sandinista military leadership in Leon, after consulting with labor groups, businessmen "and other democratic sectors" had drawn up a list of five persons to present to the citizens of what is Nicaragua's second-largest city.

Leon's citizens were called this afternoon to the city's central plaza, Hassan said, where they were asked to approve - by voice vote - the five persons on the list, who will serve as the civilian authority in the war-shattered city. The list, Hassan said, "was ratified unanimously."

He added that in an earlier election in Masaya, another Nicaraguan city, two of those on the list presented by the Sandinista authorities were rejected.

The junta also announced a series of measures designed to speed the country's return to normality three weeks after the new government came to power and imposed emergency rule in the wake of Anastasio Somoza's defeat.

In another step, the junta announced that La Prensa, an independent newspaper that long opposed Somoza, will reappear in the near future, probably next week.

The junta also said privately owned radio and television stations will be allowed back on the air after Aug. 22. Junta member Daniel Ortega said, however, that before then government officials will meet with station owners and journalists "to discuss the best way for them to function."