The Department of Agriculture has drawn up plans to cut grain production by paying farmers not to grow crops on land that has soil erosion problems, Secretary of Agriculture Bob Bergland said yesterday.

Bergland said there is "all kinds of pressure" to put the plan into effect to protect farmers from the loss of income resulting from President Carter's decision to limit grain exports to the Soviet Union.

But Bergland said he is opposed to it and considers it unlikely to be used unless other efforts to support farm prices are unsuccessful.

Grain prices on the Chicago Board of Trade went down slightly yesterday, after two days of increases.

Bergland said he recommended that Carter embargo grain sales to the Soviets after he was assured that farmers would not be hurt. Since then the administration has promised to buy up all the 17 million metric tons of grain the Soviets were to buy and take it off the market.

Bergland said the administration will soon ask Congress for permission to stockpile 4 million tons of wheat from the Soviet deal and use it to feed hungry nations. The agriculture Department already has authority to buy the grain, but to store it for foreign aid projects.

As explained by Bergland, the plan to cut grain production would have the government rent land from farmers. The best crop-growing acreage would continue to be planted, but land that is easily eroded would be taken out of production.

Bergland denied reports that a decision to pay farmers to take land out of production will be made before next Monday's Democratic caucuses in Iowa, the leading corn-growing state. He said the final decision is at least two weeks away.

Paying farmers not to grow grain has not been a major part of federal farm policy for several years. The government offered farmers a small crop land-diversion program last year, but only one in five signed up.

Bergland said he expects the International Longshoremen's Union to heed a request by the president to load some Soviet ships with grain.

The embargo allows the Soviets to buy a limited amount of grain, but the dock workers have refused to load any. A union spokesman said there has been no decision to change that policy.