THE WORLD'S wheat exporters, after negotiating for four years to set aside reserves to combat the next big international food shortage, have come up with almost nothing. They had an agreement, to be sure. But it was an agreement to make a small amount of wheat available - 15 million tons, which would not even meet world grain requirements for one week.And that pittance was not to become available until the scramblings of hungry nations had driven the world price outrageously high. Small wonder the developing countries turned the plan down.

Such a calamitous breakdown of the international system was not supposed to happen. After the crisis of 1972-1974, in which hugh American grain sales to Russia followed by widespread drought drove up prices and produced worldwide privation, the United States launched an international effort to prevent a repeat performance. Interdependence was to be made real. The effort involved encouraging other countries to grow more food themselves, and also spreading a safety net of reserves. But good weather came and with it good crops and, meanwhile, world food demands rose. The wheat-reserve talks finally came down to a contest between producers and consumers. The producers were ready to see a floor put under the prices they receive in a falling market, but they wanted no suggestion of a ceiling - and reserves held off the market for emergencies are a kind of ceiling - on prices in a rising market. Neither the consumers who do the buying in normal times nor those who need help in bad times had much say.

In this fashion is the world poised for the next famine and the next price run-up. Sooner or later - it always happens - the weather will turn foul, crops will be poor, importers will bid up food prices. The countries and consumer groups with means will get by; the others will not. In many places, funds needed for development will have to be diverted to food; funds needed for food will have to be stretched to cover the higher prices. The United States and the other exporters will consider planting more acreage, but that will not take care of the emergency.

American officials, their good intentions defeated by producer and budgetary pressures, contend that domestically held reserves are adequate. But a single Soviet crop failure could wipe out these stocks and if, as earlier in the 1970s, there were two failures in a row, disaster would ensue. The United Nations' Food and Agriculture Organization has improvised an emergency "action plan" based on "the good will of governments." Good will and, in an emergency, something like $210 will get you a ton of wheat.