Inside Report (5)

The Soviet Union's loss - on its -disastrously poor wheat harvest this year - is the US Treasury's gain. The Department of Agriculture will pay US wheat farmers some $400 million in -''deficiency payments'' to offset low grain prices. But if the Soviets weren't buying heavily on the US market, these payments could have topped $1 billion.

The record-breaking US wheat harvest of 2.75 billion bushels means that the farm price is expected to stay well-below last year's average of $3.96 a bushel. But Soviet grain purchases should guarantee export -markets for 70 percent of this year's crop.

Prices also are strengthened by a Senate vote banning any further embargoes that single out farm products.