Two years after the word emerged from the shadow of famine and food scarcity, a new world food crisis plagues governments at home and abroad.

This new crisis is one of too much wheat, not too little, and its dimensions and statistics are the reverse of those that prevailed when food supplies were disrupted from 1972 to 1974, and when some economic prophets predicted that the world might be running out of food.

A mighty torrent of grain engulfs storage depots as the harvest of 1977 sweeps across North America, Europe and Western Siberia. The world now has 40 million to 50 million metric tons more wheat on hand than it will need in the coming year, and even countries that normally live from harvest to harvest have a comfortable margin of grain.

India - a country that often faced food deficits in the last two decades - still has 18 million tons of food stored away as it harvests more rice and wheat.

And Bangladesh - the focal point of famine relief efforts in 1974 and 1975 - has begun repaying its wheat debts. In May, it bought 40,225 tons wheat, but ordered it shipped to Russia as partial repayment of 200,000 tons it received earlier on loan.

In the United States and canada, which together control almost two-thirds of the global wheat trade, prices are sliding down toward the level they were in early 1972, the point at which world food price inflation began.

There is a strong element of good news in this turnaround of a situation that threatened some countries with famine and squeezed the treasuries of others that depend on imported wheat.

But food experts warn that the situation also poses grave dangers. One of these is complacency about the lingering problem of world hunger. The full grain bins do little to alleviate the malnutrition of an estimated 450 million people who have no money to buy food or who live beyond the reach of food pipelines.

"We are in the eye of the storm," a White House official said.

According to E. A. Jaenke, a Washington food consultant, "the world is rapidly approaching another food crisis which may well be of even greater magnitude than the last crisis of 1972 to 1974.

The main reason for such gloom in the midst of apparent plenty is the absence of any international system for evening out the boom-and-bust cycles in the wheat trade.

Advocates of an unregulated free market in grain say that supply and demand is the best controller of the food supply. In the short run, the forces of the marketplace could push grain prices still lower. But these same forces are also likely to push prices up later on. When that happens economies of countries all over the world can be strained.

A 1967 agreement between wheat exporters and importers established ceilings and floors on wheat prices. But that agreement quickly collapsed, leaving countries exposed to pressures that sent wheat prices from $1.75 a bushel to more than $5 a bushel between 1971 and 1974.

The Carter administration has made a general pledge to support the renewal of such a cooperative system. Secretary of Agriculture Bob Bergland said last week that he favors "guidelines" under which governments would have to take certain controlling actions when prices reached agreed-on levels.

One element of this system might be grain reserves which governments accumulate when prices get too low and release when they get too high. However, the administration plan is still in the drafting stages.

Substantive talks on a food reserve will not begin until later this year. In the meantime, Bergland admitted, there is nothing to prevent a "free-for-all" in world wheat markets this summer.

As domestic pressures to unload the costly-to-store surpluses mount in exporting countries, there is an immediate threat of economic confrontation.

Both Bergland and the Otto E. Lang, the Canadian cabinet official in charge of grain marketing, have expressed hopes that a price war can be avoided. Nevertheless, pressures are increasing and some officials at the U.S. Department of Agriculture are still angry at Canadian tactics last summer.

Faced with a bumper wheat crop, falling world wheat prices and the costly prospect of stroing much of the unsold grain for months, the Canadians secretly sold 4 million to 5 million tons at up to $13 a ton below the American price.

The wheat was sold to international grain companies, which channeled it to the Caribbean, the Philippines, Indonesia and Europe.

Minnesota wheat farmers who tried to sell their wheat during this period often found there were no buyers at the prices quoted in American grain exchanges. Farmers were puzzled - until word finally leaked out that the Canadians were using the private companies to funnel wheat into markets often served by American wheat growers.

When the U.S. agricultural attache in Ottawa asked for details about the selling prices, the reply was "We're not going to tell you that."

A few months later, Argentina began marketing its wheat below the U.S. price.

In the short run, importing countries would benefit from another round of price-cutting this year by the major exporters - the United States, Canada, France, Australia and Argentina. But food experts say that depressed wheat prices could result in adjustments that send prices spiral ling upward again in the absence of international controls.

Bergland said this week that if the wheat buildup continues in this country through Aug. 15 he will seriously consider having farmers idle between 10 and 20 per cent of the nation's 80 million acres of wheat growing lands.

That would be a step back to government limitations on wheat production which existed before 1972. Such a step would be dictated by domestic political realities here. But it would be a reluctant one for Bergland because of its possible impact on world hunger later.

According to Harry E. Walters, assistant executive director of the World Food Council in Rome, the current wheat price in the United States is "much lower" than the price in 1971 when the farmers' increased costs of fertilizer, pesticides and fuel oil are considered.

And the significance of bargain wheat prices was demonstrated in 1972 when Americans learned that large grain stocks can be depleted rapidly - with results that effect people's pocketbook. Wheat prices were under $2 a bushel then, and had been for years. But governments abroad wanted to buy more American food to improve the diets of their populations, and the Soviet Union, in particular, took advantage of the bargain prices to launch a raid on the U.S. grain stocks. Food prices inflated steadily from 1972 to 1974.

Wheat prices are determined mainly by how much buyers and sellers think will be left over right before farmers start their new harvest. If a great deal is left over, as is the case this year, prices stay now. But some experts believe that when American wheat farmers start-harvesting their crops in the middle of 1978, somewhat less food will be in the grain bins than is there. There are a number of reasons for this assessment.

For one thing cheap wheat is certain to increase demand for it. The International Wheat Council in London says the wheat trade will increase by at least 8 million tons next year because wheat is now such a bargain. Also, American farmer have begun using more of it to fatten their hogs, cows and chickens.

Developing countries abroad have the largest stake in preventing a new price spiral. They buy about 40 per cent of the wheat exported.

Their requirements for wheat to feed growing populations cannot be reduced easily. Bread made from imported wheat - a food that was almost unknown in Asia before World War II - is now a staple in the diets of city populations of Korea, Taiwan, the Philippines and Indonesia.

And for some regimes overseas, the ability to obtain this wheat as reasonable prices is a matter of political survival. American and Arab officials said last week that Egyptian President Anwar Sadat could face political turmoil at home if wheat prices rise sharply again.

Wheat is a crucial component of Egypt's fragile food system. Egypt buys the wheat from abroad and resells it to local flour millers for less than it cost.Food subsidies of this kind cost the government nearly $1 billion a year.

Rioters forced the Sadat government to rescind a threatened end to subsidies on bread, vegetable oil and tea in January. If the cost of imports increases, the government either will have to increase the subsidies even more or face possible new demonstrations.

Policymakers say a way to spare Egypt, other nations and U.S. consumers from the impact of a sudden rise in wheat prices would be to create an International stabilization plan.

SOme officials in Washington say the condition establishing such a system are more favorable than at any time since New Dealer Henry A. Wallace championed an "ever-normal granary" in 1933. Wallace never achieved his dream of getting nations to cooperate to prevent the ruinous cycle of scarcity and surplus in the global wheat trade.

The Carter administration, however, has indicated broad interest in commodity agreements, including one for wheat. Wheat prices fluctuated 45 per cent between 1971 and 1976.

Canada and the United States both want to maintain a system where buyers abroad rather than taxpayers at home pay for the cost of continuing wheat production in North America.

The United States would have to pay private companiex subsidies if world wheat prices slipped below the present $2.25 a-bushel support price.

Similarly, the Canadian government would have to make payments to prairie wheat farmers if prices decline below the guaranteed minimum of $3 a bushel.

The American export subsidies were sharply criticized in Congress in 1972 on grounds that the government subsidized wheat that the Soviet Union would have bought anyway.

Canada's Lang and Bergland agreed informally in February to try to keep prices above these levels. That meeting of the minds caused talk abroad that the two big wheat exporters were planning a wheat cartel. Lang denied that, saying both countries wanted wheat importing countries to join any price stabilization plan.