On the fifth day of his state visit to the United States, President Julius K. Nyerere of Tanzania turned from the political questions of southern Africa to the question of his own country's basic agricultural development needs.

Fertilizer and rural electrification were uppermost on his mind during his one-day tour of Tennessee. At a briefing by Tennessee Valley Authority officials here, Nyerere listened thoughtfully to a rundown of TVA agricultural projects.

When told that fertilizer prices were going down, he appeared startled.

"Why haven't I been the benefit of this?" Nyerere asked, moving to the edge of his seat.

"It just hasn't reached you yet," replied Gov. Ray Blanton, who sat next to Nyerere during the afternoon briefing at the Arnold Engineering Development Center and later accompanied him to a dam project. Blanton added that the price decline was recently reversed because of a scarcity of natual gas for chemical production.

The 15 million people of Tanzania depend on agriculture for their livelihood. Most of the farmers live in a system of collective villages introduced by Nyerere 10 years ago - a system he candidly admits has been hampered by public inertia.

"We have made fertilizer but the people were throwing it away and whitewashing their houses with it," said Nyerere, whose country produced 100,000 tons last year. "But recently the farmers have started stealing fertilizer. We haven't prosecuted because we think we have made some progress."

Nyerere arrived in this central Tennessee city of 17,000 at 1 p.m. from a two-day tour of California. In California, as in two days in Washington last week, Nyerere was questioned about political and racial strife in southern Africa. But in his four hours here today he was immersed in conversation about the agricultural and economic development of his country, one of the world's poorest.

From Tullahoma he flew to Nashville where he attended a country music concert by Ronnie Milsap and Charlie Pride at Opryland and a Blanton dinner and reception.

Eight miles north of Tullahoma on the Duck River, Nyerere visited Normandy Dam, TVA's newest. The Tanzanian president and his aides expressed great interest in the construction of dams. Currently Tanzania is developing ideas for a Rufiji Basin Development Authority, a 72,000-square-mile project, similar to the Normandy Dam, criticized by conservationists, is designed mainly for recreation rather than area development; it does not generate electricity. The Tanzanian Rufiji project emphasizes irrigation, flood control and power generation. But as an earthern dam Normandy was chosen for the Nyerere visit because of its similarity to projects in developing countries.

Nyerere is scheduled to tour several farms in rural Georgia Tuesday and attend a reception in Atlanta given by Gov. George Busbee.