Agriculture Secretary John R. Block, on Capitol Hill to unveil his 1981 farm bill proposals, got a class-action reminder yesterday of the sensitivity of congressional toes when stepped on.

The House Agriculture Committee listened patiently for most of the day as Block outlined details of his program, but then it left a clear message: Congress still intends to look out for its farm friends back home.

The man from peanut country, Rep. Charles Rose (D-N.C.), was perturbed by Block's plan to end the peanut acreage-allotment system and made it plain he would try to reverse the tide.

Rep. Pat Roberts (R-Kan.), the man from wheat country, was not pleased with the administration's intention to have only modest price-support increases for grain farmers and questioned its handling of the farmer-held grain reserve program.

Reps. Tom Hagedorn (R-Minn.) and Byron Dorgan (D-N.D.), concerned about decreasing numbers of farmers, expressed doubts about approaches they saw benefiting large farm operations at the expense of smaller, more marginal farms.

The man from fresh vegetable country, Rep. Tony Coehlo (D-Calif.), fretted about reports that the administration might try to revamp the marketing order system that controls the flow of specialty crops to consumers and regulates prices.

Sugarland's man, Rep. Jerry Huckaby (D-La.), was unhappy that Block had not included sugar price supports in his plan. Dairy advocates, Reps. Floyd Fithian (D-Ind.) and Steve Gunderson (R-Wis.), were anxious about dairy price support cuts.

And through it all, just about everyone fussed at Block about the administration's refusal to lift the partial embargo on grain shipments to the Soviet Union. Block agreed that the embargo has undermined farm markets, but he repeated his optimism that the administration won't leave it on forever. b

Block's testimony will be the basis for congressional development of a bill governing basic farm programs, but Chairman Kika de la Garza (D-Tex.) said the secretary's delay in appearing before the committee had added to the difficulty.

Under congressional budget rules, the bill must be completed by May 15, a target that de la Garza said can be met only "if the administration is not welded" to its program and is "willing to compromise."

Block was to have announced his farm program last week, but some details were not final, and the administration feared a congressional backlash against its crash effort to stop a mandatory April 1 increase in dairy price supports.

The program Block laid out yesterday adhered closely to positions he has talked about since January -- an emphasis on export development, fewer controls on farmers, only modest commodity support increases and an end to target price payments (direct subsidies) to grain producers.

The secretary said the new dairy proposal would hold the price support at 70 percent of parity for the year beginning Oct. 1, with upward or downward adjustments if needed to keep a balance between spply and demand.

Unless the present mandatory-increase system is changed, the government will spend at least $908 million next year to prop up dairy farmers, Block said.

He said the dairy proposal -- which drew strong objections from the committee -- was part of the administration's overall objective of reducing government costs, while assuring continued growth in agricultural productivity generally.

Another aim is to help U.S. farmers take advantage of strong and growing world demand for food products without "a major and unwarranted government presence in the marketplace," he said.

As a part of that approach, the secretary proposed increasing by $300 million the export credit program to develop markets that otherwise might not be available in Third World countries.

Block said the administration will not have a comprehensive soil and water conservation proposal ready until late 1982, but he agreed under pressure from Rep. George Brown (D-Calif.) to speed up the timetable.