American aid has reached into this village nestled in a parched hollow of Africa's semiarid Sahelian zone that is struggling to sustain human life even as paradoxically, its population is burgeoning.

The Sahel, fending off the Sahara Desert to the north, inadequately supports some 60 million people today with the help of food from abroad. That number is expected to double in 30 years. But within half that time, the estimated 3 percent annual population growth of families that survived a devastating 1968-74 drought will have vastly outstripped the region's capacity to support them.

The lifetime for the 783 villagers here may be the U.S. aid program trying to change traditional farming methods and improve yields. In turn, thousands of similar villages may benefit from similar international efforts.

The question for the Sabel's people and their poor governments is what will happen when the funds necessary to subsidize these programs dry up. The outlook improved last week when the Reagan administration pledged a 30 percent increase in U.S. aid programs to Africa, but the international funding still remains precarious.

Experts estimate that it could take 25 years to achieve self-sustaining food production in the Sahel.

Ironically, part of the Sahel's problem results from the international food aid and health programs.

The population growth has accelerated the cutting of the Sahel's essential, scarce forest cover as people seek fuel for cooking. Vital top soil, without tree roots to hold it, is blown away by the harmattan, or Saharan dry-season wind, that expands the patches of desert where crops once grew in the rainy season.

The amount of cultivable land, always limited, is shrinking.

Before the drought began in 1968, farmer Yacouba Oumarou -- one of the first participants in the training program -- gathered firewood with his brother during the six-month dry seasons. They took it by camel 50 miles to Niger's capital to sell. They then bought food to supplement their own crops.

"Even back then," Oumarou said, "it was very difficult to find firewood concentrated in an area. We had to go farther and farther away. . . A lot of land was killed.

Sahel, an Arabic word meaning border, defines the stretch of trees and seasonal vegetation up to 600 miles wide, running 2,600 miles from Senegal to central Chad. It includes land of Cape Verde, Gambia, Mauritania, Mali, Upper Volta and Niger.

Of the eight Sahelian countries, Niger has been most successful in restoring farm output since the drought. In grain production, it has surpassed the 1.5 million tons needed annually. This grain self-sufficiency was accomplished despite large population growth: from 3.5 million in 1964 to 5.5 million today.

But Niger's 900,000 farmers are still dependent on the rain. One of the Sahel's prolonged cyclical droughts could wipe out their recent gains. While Niger is sustaining life, much remains to do in improving it.

The life expectancy of a child born is Sadeize-Kouara, for example, is 42 years, if he lives past age 5. Of some 250,000 babies born in Niger in 1980, 40,000 died in their first 12 months. Of those that lived, 50,000 will die before the age of 5 from curable diarrheal diseases and chronic malnutrition.

Many Niger adults suffer from untreated festering sores, respiratory diseases, chronic diarrhea and eye infections that lead to blindness.

Niger earns foreign exchange by exporting uranium and uses the revenue to finance food development, health and education projects.

When uranium prices were high, Niger went $750 million in debt to finance a five-year development plan. But last year, the world price for uranium plummeted and left the financing of Niger's plans in question.

The loans "may have very negative effects on our economy" when they begin coming due in the mid-1980s, said the military head of state, Col. Seyni Kountche in an interview.

"But this is an effort without a price tag for us," said Kountche, whose government's annual budget is $336 million. "We do have to carry these things out whatever the debt is we run into."

Only 12 percent of Niger's 490,000 square miles is considered cultivable. All of this is under cultivation and population pressure is pushing farmers onto marginal land.

Development experts say most of the sandy Sahelian soil is fragile because of low water-holding capacity, limited ability to retain soluble chemical fertilizers and high susceptibility to wind and water erosion.

In 1979, the U.S. Agency for International Development office in Niamey, the capital of Niger, began a $19 million five-year program to train 2,000 farmers in growing more grain while strengthening the fertility of their farmlands.

During a six-month growing season, the farmers and their wives live at a trainging center learning -- most for the first time -- to use animal droppings as fertilzer, to mix it with chemical fertilizers and plow it all into a field with an ox-drawn plow. The farmers are also taught row planting, for better yields through easier weeding, and use of high-quality hybrid seeds.

Because he is a land-rich peasant, with 30 acres, more than four times the average farm in his area, Oumarou was approached by the village chief to go into the American training program for the 1979 growing season.

The expectation is that the trained farmers will return to their villages and pass on what they have learned.

At the training center, Oumarou, 35, said, he learned about manure, chemical fertilzers and use of cattle for plowing.

Last spring, when he began to plow 10 of his acres with the oxen, "my family said I was crazy," he recalled. "They told me that I just didn't want to work and that plowing with oxen wouldn't work."

Last fall, Oumarou said, he harvested much more on the 10 acres than was produced on the 20 acres his family worked in the traditional manner. Now, he said, they are convinced the new methods work better.

Of the 17 peasants graduated from the first training class, only Oumarou and another farmer had significant increases in their food production. The others did not fully trust and use the new methods and harvested the usually small yields, said a program official.

With his extra production, Oumarou could stay home this dry season and supervise construction of a mud-brick house he financed with grain sales. But he still had not repaid the $250 due as the first installment on the $1,000 loan he received in the form of the oxen and supplies.

The U.S. aid director for Niger, Jay Johnson, said a primary objective of the program was raising seed production above a family's normal needs. "The farmers store the grain to use as food in case of drought or for planting the next season's crop," he said.

At the start of the May rainy season, Sahel peasants often replant from their grain stores four or five times as the rains start and then die out, Johnson said.

Niger's illiterate farmers, whose average yearly cash income is $200, cannot afford to buy oxen, which cost $500 a pair, a plow, fertilizer, hybrid seed and a donkey-drawn weeding hoe, so these are subsidized by the aid program and the Niger government. The farmer is expected to repay about $1,000 plus 11 percent interest to his farming cooperative in four years.

One knowledgeable development official saw problems with the training program. The technological improvements, he said, increase the farmers' yields an average 10 percent, too little to enable him to pay back the loan.

The expert said oxen are not profitable on a farm of less than 15 acres but 92 percent of the Niger's farmers have seven acres or less.

He said most of the increase in Niger's food production came not from such training programs but rather from the government cutting taxes and the peasants then quickly turning over land that had been used for cash crops, such as cotton, to food crops.

If the aid program ends in the mid-1980s, the expert said, the farmers will not be able to afford the costly chemical fertilzer, carted overland 750 miles into Niger. "The Niger goverment can't afford to subsidize the chemical fertilizer and withou it, the [hybrid] seeds won't work," the expert said.

"It is true that most of the farmers are barely [cash] economy," said aid director Johnson, "and the government could not subsidize fertilizer for all of Niger's farmers." But the goal of the program, Johnson continued, "is to get farmers up to monied levels so that they can afford to buy unsubsidized materials."

"If the program spreads training to enough farmers in places [like Sadeize-Kouara village] over the next couple of years, I think it'll work," Johnson said.