- Nobel Prize-winning scientist Norman Borlaug told Vice President Mondale today that the United States and other governments should give top priority to at least doubling world food production in the next 40 years.

"If we are to look at the future, we have to look at it with fear," Borlaug warned. "In the next 40 years, another 4 billion people will swell the world population at the current growth rate. Doubling food production is a trememdous undertaking. It cannot be achieved with the miserly and discontinuous support invested in world agriculture in the last 50 years.

The American scientist, often described as the "father of the green revolution," briefed Mondale on the research carried out at the International Maize and Wheat Improvement Center, outside the Mexican capital, which he directs. He won the Nobel Prize in 1970 for developing a dwarf strain of wheat that multiplied output in India and Pakistan.

Borlaug became passionate as he stressed the need to turn the current 3.3 billion metric tons of world food output into 6.6 billion tons in such a short time. "Failure to achieve this goal, will plunge the world into economic, social and political chaos," he said.

Borlaug also argued forcefully against the U.S government's donations of surplus food under PL 480, often granted without demanding fulfillment of agreed work projects or the agricultural developments plans from the receiving countries.

"I've seen it happen time and time again in countries which say their food problem is now resolved [with U.S. surplus food] and start worrying about a different sector of the economy," Borlaug said.

Such donations, he stressed, only serve to diminish food production.

Mondale seemed deeply interested in the agricultural expostion, which ended the official half of his visit to Mexico. This afternoon, he traveled to Yucatan, accompanied by his wife Joan and his son William, to visit Mayan ruins. He is to return to Washington Sunday.

The day and a half in Mexico City was seen here as more of a curtain call than a working trip for Mondale, who visited Canada earlier in the week. "Officials on both sides were very euphoric about their good relations, but precious little was done," one prominent diplomat here remarked.

According to reliable U.S. sources, Mexican President Jose Lopez Portillo has reacted "cautiously by positively" to Mondale's offer for a vast U.S. supported multilateral development project. Such a project, the outline of which must be developed by Mexico, would be aimed at the poor areas from which millions of migrants illegally cross into the United States seeking work.

A multilateral loan, to be provided by the World Bank and the Inter-American Development Bank, would be politically acceptable to Mexico, which refuses outright U.S. aid and has shown no interest in the Carter administration's proposal for a joint $2 billion development fund.

"Mexicans are very difficult," sighed one key U.S. official. "They need help, but they won't accept any aid."

On the issue of Mexican natural gas sales to the United States, which are suspended in a squabble over price, Mondale told reporters he had described "the current status of our energy package" to the Mexican president, "but we did not get into natural gas prices at this time."

In private consultation, Mondale and Lopez Portillo reportedly agreed on general principles regarding human rights without Mondale's having mentioned the frequency alleged Mexican violations.

Earlier this month, Martin Ennals, the head of Amnesty International, met with government officials here to express his concern over the "more than 100 political prisoners and over 300 missing persons" in Mexico.

A key US. official explained that the issue in Mexico is "a very touchy one and, compared to so many other countries, the human rights problem here is relatively small."