The assignment of Stephen B. Dewhurst, who has juggled numbers for 20 years at the Agriculture Department, was to take his sheaf of papers and his dreary news into a congressional shredder. His goal was to try to emerge in one piece.

The news carried by Dewhurst, USDA's soft-spoken budget director, was a description of the administration's plans to reduce agriculture spending this year and in fiscal 1987 by a total of about $10 billion.

Dewhurst survived his encounter at the House Appropriations subcommittee on agriculture this week, but barely.

Reps. Jamie L. Whitten (D-Miss.) and William H. Natcher (D-Ky.), whose 78 years of combined service in the House gives them unusual clout, showed Dewhurst some sympathy, but told him they weren't buying his news.

Whitten, chairman of the full Appropriations Committee, expressed dismay at some of the proposals and peppered Dewhurst with sarcasm. "My questions have been facetious because the budget is so ridiculous, in my opinion," Whitten said.

Whitten, who was elected to Congress a month before Pearl Harbor was bombed in 1941, said he had supported the administration's defense-spending increases, but enough was enough. "We had better learn that food, clothing and shelter are the basic things," he said.

Natcher, 32 years on the subcommittee, led Dewhurst through questions revealing that the major cuts were proposed by the Office of Management and Budget rather than USDA. "If we took this budget to the floor, we couldn't pass it," Natcher said. "The House wouldn't accept it."

If those and other subcommittee members' remarks were fair indication, the administration's plan to cut the budget by slashing some of the most popular USDA programs would appear headed for serious trouble on Capitol Hill.

Roughly $34 billion of the department's budget will go to farm subsidy and nutrition programs, following formulas set by law, so most of the cuts would come from other USDA service operations. These are some of the highlights -- or lowlights, depending on one's vantage point -- of the 1987 proposals:

Agricultural research would increase by $35 million but the budget would cut the cooperative state research program $29 million by zeroing out special research grants and special animal health and disease research.

The Cooperative Extension Service would be cut by $187 million, ending programs such as pest management, farm safety, nutrition education, pesticide impact studies and financial management.

The Animal and Plant Health Inspection Service would be cut by $49 million; the Agricultural Marketing Service would lose $365,000; the Office of Transportation, $1.1 million, and the Rural Electrification Administration, $131 million.

Farm operating loans would increase through the Farmers Home Administration (FmHA), but almost all of its other rural development and housing programs would end. About $200 million worth of soil, water and forestry conservation programs would also be killed.

Dewhurst said other big savings could occur if Congress agrees to allow some inspection programs to be financed with user fees -- a move that has drawn fire from the meat, poultry and grain industries.

"Have you got somebody stashed out who will introduce that legislation for you?" Whitten asked.

"The objective is to have it all introduced by the end of the month. I don't know who will introduce it," Dewhurst said.

"Well, it's not your job," Whitten said, "and you're not sorry, are you?"

Steve Dewhurst just smiled.