Poland's military ruler, Gen. Wojciech Jaruzelski, has promised measures to boost agricultural production and blamed antisocialist activity, "past mistakes and neglect" and Western economic sanctions for Poland's inability to feed itself.

Jaruzelski, in a speech yesterday that was published here today, said the government would use "the instruments of martial law" to increase production of agricultural resources by industry. He also hinted at moves to consolidate Poland's privately owned farms, saying that huge reserves could be released by bringing neglected and inefficient farms to "full productivity."

Jaruzelski's remarks coincided with a statement by leaders of the suspended Solidarity trade union in Warsaw warning of "explosive outbursts" because of food shortages and high prices. The statement said social tensions could be controlled only through reconstitution of an independent trade union movement.

The government has complained that many private farmers, who own 70 percent of Poland's agricultural land, have been hoarding grain rather than selling it to the state. But Jaruzelski did not threaten the farmers with compulsory deliveries--a measure often used by Communist states in times of food shortages.

Most agricultural experts say compulsory deliveries, while easing short-term shortages, would have serious consequences for the future. One farmer said, "It's a weapon they can only use against us once."

In his speech to the Central Committee of the United Peasants' Party, which is allied with the Communist Party, Jaruzelski also said that "the powerful United States has declared war on Polish chickens" and appeared to be winning. Officials have said the Polish poultry industry is in danger of collapse this year because of a U.S. embargo on credits for grain exports to Poland.

"It is of course possible to defeat Polish chickens, but it is impossible to defeat Poles, Polish workers and peasants," Jaruzelski said.

The Solidarity statement, in a clandestine bulletin circulating here, was signed by Zbigniew Bujak and Wiktor Kulerski, chairman and vice chairman of the union's Warsaw branch. Both are believed to be in hiding in the Warsaw region after escaping detention following imposition of martial law.

The Solidarity officials described a government-sponsored debate over the future of trade unions in Poland as "outrageous," since it was taking place as union leaders remained "interned, arrested, or sentenced" and some activists had been "beaten, maimed, or murdered."

"The present economic situation and the burdens it imposes on families' budgets will cause social tensions and could lead to outbursts in many parts of the country," the statement said.

Despite earlier signs of progress, contacts between Solidarity officials and the government appear to have run into difficulty over the past few weeks. The reasons are not clear, but Western analysts speculate that the Soviet Union and Polish hard-liners could be opposing moves toward national reconciliation.

Recent political activity has centered on attempts to revive the economy. This week the government said coal production over the first quarter of 1982 was up 6.2 million tons (about 15 percent) from the same period last year to a total of 47.4 million tons.

The increase in coal production, largely attributed to compulsory Saturday work, is virtually the only bright spot in a generally bleak economy. Most factories have had to cut production sharply because of the lack of imported raw materials and parts.