MOSCOW, JULY 26 -- Russian President Boris Yeltsin appealed to farm workers today to prevent a food-shortage "catastrophe" in the largest Soviet republic by harvesting this year's crops as efficiently as possible.

Yeltsin's plea was the latest official effort to increase food supplies in expectation of what Soviet analysts predict will be only a modest harvest throughout the country this year. Food is rationed in many parts of the country, and the Kremlin is urgently seeking foreign credits to buy billions of bushels of wheat overseas again this year.

As an incentive, Yeltsin said the government of the Russian republic would issue special "Harvest 90" coupons to agricultural workers -- from farmers to tractor drivers to food processors -- allowing them to buy consumer goods that have been in short supply. Details of the coupon program will be published in the coming days, he said.

"The existing food situation in our republic is critical," Yeltsin said in an appeal published on the front page of Sovyetskaya Rossiya, the republic's official newspaper. "To prevent a catastrophe, we must improve it immediately."

Yeltsin said a good harvest is expected in nearly all parts of Russia, by far the largest and most populous of the 15 Soviet republics, "but we have to gather it carefully, preserve it and get it onto the table of the Russian people." The U.S. Department of Agriculture has forecast a Soviet grain harvest of about 215 million metric tons, slightly higher than last year's 211 million tons but not as high as Soviet officials had hoped to meet the needs of a growing population.

Yeltsin acknowledged that farmers had grown tired of such pleas and that they need more fuel, more workers and a better transportation network. He blamed the country's agricultural woes on "the careless experiment started on our long-suffering land" by former Communist rulers and said farmers should have more freedom to make independent decisions and sell their surplus produce to whomever they want at whatever price they can negotiate.

Yeltsin said the bonus coupons will be issued both for produce that is required to be sold to the state, as well as for surplus produce sold for profit.