The Carter administration defended its suspension of grain sales to the Soviet Union before skeptical members of Congress yesterday and offered a few new sweeteners to make the partial embargo more palatable to farmers.

Cutting grain sales to the Soviets "will mean chicken shortages by springtime and pork shortages by summer" for the Russians, said Secretary of Agriculture Bob Bergland.

Appearing before the Senate Agriculture Committee, Bergland repeated the administration's promise that farm income will not suffer from cancellation of sales of 14 million tons of grain to the Soviets.

Despite the administration's pledge to buy the Soviet grain and take it off the market, corn prices have dropped 10 to 15 cents a bushel and Soviet Chairman Herman E. Talmadge (D-Ga.), several committee members urged the White House to pay farmers not to grow grain this year.

Bergland, who previously has said he opposes doing that, appeared to keep the possibility alive. "We have full legal authority to offer a paid diversion program," he said. "We will not hesitate to implement" it if necessary.

Bergland disclosed that the Agriculture Department will announce today another alternative technique for raising farm income. The department will waive the interest that farmers have to pay on money they borrow against their crops under government farm loan programs.

That will not only save farmers money, it will also make it more attractive for them to put their crops into the government grain reserve, thus keeping the crops off the market and raising prices.

Bergland said the White House is also increasingly by $200 million the money it lends foreign governments to buy U.S. grain for 1981. He asked the committee to vote a $196 million increase in money to buy grain for the Food for Peace program under P. L. 480.

Bergland also urged approval of a plan to create a strategic grain reserve, which has been stalled in Congress for two years.

But the secretary said the administration is still opposed to a plan pushed by Talmadge and other farm state senators to have the government buy grain and stockpile it to make alcohol for fuel.

Bergland also disclosed that, despite the embargo, the administration plans to let the Soviets buy some U.S. grain later this year. They will be allowed to buy 6 million tons, the minimum amount the U.S. promised in a five-year trade treaty that still has a year to run.