ONE potato, two potatoes, 41.7 billion pounds of potatoes! That's the size of this year's United States spud crop, an all-time high.As a result, consumers are paying less for fresh potatoes at the grocery store. But the price of French fries won't change on menus at fast-food drive-through lanes. Restaurant chains purchase potato products made from contract-grown potatoes in order to keep costs and supplies stable. Perfect weather in the major growing areas coaxed record yields out of a record number of planted acres, bettering the previous highs in Idaho, North Dakota, and Washington State, says Gary Lucier, a US Department of Agriculture (USDA) economist. Output in those states more than offset drought-induced declines from Ohio to Maine. Overall, the US harvest improved on 1985's tally, the previous record, by 3 percent and on last year's by 4 percent. Comparisons at the state level show that the industry continues to move west. As recently as 1987 Maine's Aroostook County led all other counties in potato production, according to the most recent Census Bureau data. But the state had ceased to be the leader 30 years earlier, when its 3.8 billion pounds of product was surpassed by Idaho's 3.9 billion. This year Maine grew only 1.9 billion pounds to Idaho's 12.2 billion. "I wish I knew" how low the state's harvest will go, says Bernard Shaw, commissioner of the Maine Department of Agriculture. "We didn't get any water" this year, he notes. But in addition, farmers planted only 83,000 acres. The potato industry would like to boost that back up to 100,000 acres, less than half the state's total in the 1940s. Mr. Shaw says the state declined as a potato producer when heavy machinery came into use that severely compacted Maine soil. And though the potato processing industry began in Maine, it expanded most in the West. Furthermore, Maine farmers haven't been able to market a quality product consistently. And they have a difficult time competing with Western farmers who grow potatoes more efficiently on larger tracts of land. However, Shaw says, Maine has succeeded in a niche market: potato seeds. The cold climate keeps down the aphid infestation that prevents other areas from producing their own seeds. The potato is a four-season crop in the US. California alone manages to grow potatoes year-round. Planting has just begun in Florida, Mr. Lucier says. Texas, Arizona, and Alabama will start crops in the spring, followed by Michigan, Colorado, and Delaware in the summer. That output is consumed fresh as fast as it is grown. But the fall crop is the biggest of all, last year exceeding 80 percent of the annual total. That's when the potato heavyweights like Washington and Idaho raise their crops. One in fou r US potatoes grows in Idaho. The fall crop is carried over into the following year and sold out of storage as demand warrants. The size of the 1991 crop has already depressed prices. However, it won't "destroy the market," Lucier says. Western growers will have an opportunity to ship some potatoes to the drought-afflicted Eastern market. Last year's price of $6.08 per hundred pounds will likely slip to $4 or $5, he says. At the retail level, consumers paid 32 cents per pound last December. By late summer that had risen by a dime. Retail prices have fallen to as low as 10 cents per pound. However, that will depend in part on the individual grocer, he says. Lucier says that the average American eats 127 pounds of potatoes in a year. The platter includes 50 pounds of fresh potatoes, 46 pounds of frozen potato products like French fries and hash browns, 18 pounds of potato chips, 11 pounds of dehydrated potato products, and two pounds of canned spuds. That size annual serving makes potatoes the third most important item in the US diet after wheat flour and dairy products. Unlike crops like wheat, potatoes are governed by a farm program that guarantees a minimum price and controls the amount of acreage planted. International trade in fresh potatoes is negligible, Lucier says. But exports of frozen potato products are growing, says Fred Zerza, a spokesman for J. R. Simplot Company of Boise, Idaho. US restaurant chains are making inroads into Pacific Rim countries that have trouble growing potatoes of the quality required for French fries. Demand for frozen French fries in the US market is growing at only 1 to 3 percent a year, versus 10 to 15 percent during the 1960s and '70s.