Maine potato futures tumbled the daily allowable limit yesterday in response to a government report that showed the nation's potato stocks at an all-time high for this time of year.

Potato furture prices, which have been trending upward since mid-December, lost as much as 50 cents per hundredweight in trading on the New York Mercantile Exchange.

The Agriculture Department said potato stocks ware reduced during January by only 28.9 million hundredweight, a figure at the low end of traders' guesses.

Also posting limit declines were orange juice futures. As anxieties about freeze damage to Florida orange groves abated, the contracts fell 3 cents per pound, representing $450 per contract. The current delivert closed at nearly $1.19 a pound of frozen concentrated ornage juice.

Soybean futures prices struggled up an average of 5 cents a bushel on the Chicago Board of Trade. Worries that a coal shortage might curtail production at Indiana and Ohio soybean processing plants supplied some buying incentive in the soybean complex.

Snow-clogged roads that continued to impede country grain movement in the Midwest also spurredbuying in the bean pit, as did the Agriculture Department's report of a sharp pickup in soybean exports last week.

The March soybean oil delivery gained almost one-third cent per pound, while soybean meal futures increased an average of $1.50 per ton.

Wheat advances of 2 cents a bushel in the current contract were aided by a Brazilian purchase of 300,000 metric tons of U.S. wheat.

At the close of grain trade, soybeans were 4 1/2 to 6 3/4 cents a bushel higher, with March contracts quoted at $5.65 3/4; wheat was unchanged to 2 cents higher, March $2.69 1/2; corn was unchanged to 1/2 cent lower, March $2.26 1/2, and oats were unchanged to 2 3/4 cnets lower, March $1.28.

Hog traders at the Chicago Mercantile Exchange again sold futures to take their profits, whittling those contracts by as much as $1.35 per hundredweight. Cattle and pork belly deliveries finished mixed.