Poland's fate this winter depends to a large extent on the attitudes of its 3 million private farmers, men like 35-year-old Antoni Prokopiak.

Thanks to a golden summer, Prokopiak's harvest this year has been good. But as a result of Poland's economic crisis, he is a bitter and frustated man. Since he has virtually no use for zlotys, the Polish currency, he delivers little food to the state.

Prokopiak says his ambition is to make a decent living and help feed the nation. But for the past three weeks, he has been occupying offices of the Communist youth organization here. It is the latest of a series of protests by the rural branch of the independent trade union movement, Solidarity, against the government's agricultural policies.

The militancy of Poland's private farmers is mirrored by a growing discontent in the cities over food shortages. Some of this anger is directed against the peasants who, in the eyes of people standing in line for meat, appear privileged and grasping. The much-vaunted solidarity between urban and rural workers, one of the pillars of the Polish revolution, is coming under heavy strain.

The view from Siedlce, a market city of 50,000 people in eastern Poland, is different. From here, Prokopiak's behavior seems quite normal. It represents the logical reaction of an individual entrepreneur protecting himself as best he can against inflation and empty stores.

Waiting for better times, Prokopiak is keeping his savings in that time-tested, inflation-proof rural currency: grain. What is more, if things go on as they are, he says he will have little motivation to produce for the market next year either. He will cut his crops and livestock herd back so that he has enough to feed his family -- and little extra.

It is not hard to see the consequences of all this. Private farmers own 75 percent of the arable land in Poland and, in normal times, provide 80 percent of its agricultural produce. Western food aid is minute by comparison.

Polish economists agree that the traditional ties between countryside and town in Poland have broken down. Unless they are repaired swiftly, Poland has no chance of solving its economic problems and the crisis of confidence between the Communist authorities and Solidarity is bound to deepen.

The irony is that, with mining, agriculture had been seen as Poland's best hope for rapid economic recovery. Investment periods are short, food is marketable anywhere, and private farmers -- as little capitalists -- are much more flexible than bureaucrats in a state-owned industry.

In an attempt to boost agricultural production, the government has substantially increased prices paid to farmers for milk, livestock and grains. But this has failed to produce the desired result. Last month grain deliveries to the state were 29 percent below those of October 1980, despite a 2-million-ton rise in this year's grain harvest. Pig purchases were down 38.4 percent.

In eastern Poland, where farms tend to be smaller than average, the decline in deliveries has been catastrophic. Officials in Siedlce say that almost 60 percent fewer pigs were sold to the state this fall. This has meant that it has been impossible to honor ration cards entitling town dwellers to eight pounds of meat a month.

Prokopiak admits that he has largely dropped out of Poland's official Communist-controlled economy. His produce goes either to feeding his family or as barter in private trade with other farmers.

"I need zlotys for telephone calls, that's all," he said.

Prokopiak did acquire some zlotys this year by selling a ton of grain to a neighbor for 35,000 zlotys -- about $1,100 at the artificially low official rate of exchange. He used most of the money to purchase an official chit entitling him to buy 1 1/2 ton of coal.

The deal illustrated the complexities of Poland's two-tier economy: the official state sector where prices are set almost arbitrarily and an unofficial black market where they find their own, much higher, level.

In the past, farmers feared they might be punished or harassed by party activists if they sold their produce privately. Nowadays this inhibition has all but vanished. The only incentive farmers have to sell to the state is that this entitles them to purchase limited amounts of otherwise unobtainable agricultural resources such as coal and fertilizers.

The system has become so chaotic that, in the view of most economists, it can no longer be propped up by stopgap measures. Over the past year, the official price of pork was raised from 48 to 110 zlotys per kilo (62 to $1.43 a pound). But even at the higher price, farmers still lack the incentive to sell.

Antoni Kroczek, 65, a Siedlce farmer, said there was no point selling pigs if there was nothing he could buy with his zlotys. In any case, he expected prices to rise still further. He therefore intends keeping his pigs even though they are now gaining fat rather than meat.

"It beats me why I still bother to breed pigs at all. I guess it's just out of habit and the hope that one day things will get better. Right now I can't find even the most basic essentials -- rubber boots, razor blades, nails, or fencing for my animals," he complained.

Despite the increases in the prices paid to producers, the state continues to sell pork to the consumer at 70 zlotys a kilo (91 cents a pound). On the free market, it costs the equivalent of $2.70 a pound.

Actually, however, all conversions into dollars are misleading since, on the black market, the U.S. currency trades for more than 15 times the official rate. If paid in dollars, a unit of real value in Poland, farmers are ready to sell at much lower prices.

"The authorities here are always talking about giving a green light for agriculture. What we farmers really want are greenbacks," Prokopiak joked.

In its latest effort to increase meat purchases, the government has diverted attractive consumer goods such as refrigerators and television sets to rural areas. The goods are earmarked, on a pro rata basis, to farmers who sell their animals to the state. For every 500 zlotys a farmer earns from meat sales to official buyers, he is guaranteed access to consumer goods to the value of 100 zlotys.

Officials claim this has resulted in a big rise in deliveries. But it has been bitterly opposed by Rural Solidarity on the grounds that it creates friction between the country and the town, discriminates against farmers who do not raise animals and is at best a stopgap solution.

Kroczek grumbled: "It means that in order to buy a 4,000-zloty bike, I have to sell a 20,000-zloty cow. With the change I get, I can then paper my wall. In any case it's agricultural equipment we need in the country, not more television sets."

The measure, which is to last until the end of the year, has increased the resentment of townspeople against both private farmers and the authorities. Shops in the cities are emptier than ever. A report by the Communist Party's regional committee for the Baltic port of Gdansk warned of "a complete disintegration of the market," "physical danger to shop workers" and "attacks against the administration."

Most Polish agricultural experts are convinced that the only solution is complete economic reform to restore some order to the market. But to implement such a reform successfully, the government needs credibility and trust, both of which it lacks at present.

In the meantime, the peasants of Siedlce have vowed to continue their protest.