The House yesterday adopted a new five-year farm bill, a hold-the-line measure reflecting the intense pressures of administration demands for budget austerity and farm-country calls for more federal economic assistance.

The extensive bill, with 19 sections that range from dairy and wheat price-support provisions to agricultural research, trade promotion, farm credit and food stamps, passed on a final vote of 282 to 141.

Yesterday's action came after more than a year of hearings and months of harsh debate inside the Agriculture Committee, prompted by farm-state insistence that Congress take dramatic steps to relieve the pressure that has put U.S. farming in its tightest economic straits since the Great Depression.

The debate was highlighted by frequent calls from President Reagan and Agriculture Secretary John R. Block for lower federal price supports to make American grain more competitive on world markets. Critics called Reagan's urgings a recipe for more economic woe in farm country. Farm groups pressured for more federal aid to keep farmers afloat.

Reagan's "market-oriented" proposal received only cursory consideration, but the administration won some of what it wanted on lower price supports even though it suffered a number of setbacks on other issues. The House rejected administration-backed efforts to alter the dairy, sugar and peanut programs.

Agriculture Committee Chairman E (Kika) de la Garza (D-Tex.) termed the bill "a little more flexible" than current law. But he said that it would prevent "drastic reductions of farm income" and that it "met our commitment to send farmers a message that we cared. I think we did that."

The committee's ranking Republican, Rep. Edward R. Madigan (R-Ill.), agreed in general with de la Garza that the legislation would "keep the safety net in place for American farmers."

For most of the nine major commodities it covers, the bill would lower the supports that put a floor under prices to make U.S. goods more competitive, but it would offset farmers' losses by increasing their income subsidies.

The bill also creates a new "conservation reserve" that would pay farmers for long-term idling of their most erodible lands. Farmers who plow erodible lands would be barred from receiving federal farm benefits.

The Senate is scheduled to begin debate on its bill this month. That version, at least $9 billion over budget limits, is expected to produce even more contention, with Democrats and some farm-state Republicans insisting on more generous income supports.

Before yesterday's final vote, the House also:

*Rejected, in a last-minute flurry of bitter debate, an amendment by Rep. William V. (Bill) Alexander Jr. (D-Ark.) calling for mandatory production controls to reduce crop surpluses and force prices up. The amendment, strenuously opposed by the administration, failed on a 368-to-59 vote.

*Defeated, 230 to 195, an amendment by Rep. Thomas E. Petri (R-Wis.) that would have abolished the federal tobacco-support program.

*Reversed itself after adopting an amendment by Rep. George Miller (D-Calif.) that would have barred any aid to farmers who did not provide field sanitation facilities for workers. His amendment also required that all farmers employing 10 or more workers provide drinking water, hand-washing facilities and toilets in their fields. A roll call demanded by Rep. Robert S. Walker (R-Pa.) overturned the earlier vote, 227 to 199.

Although the measure is designed to hold farm program costs within their $35 billion budget limit over the next three years, it contains at least one section -- a dairy surplus-reduction scheme -- that has drawn threats of a veto.

The bill would allow dairy supports to rise slightly, but it provides for a farmer-financed "diversion" that would pay producers to cut milk output and reduce the surpluses the government must buy. A counterpart Senate bill calls for straight cuts in price-support levels to reduce surpluses that have cost the government more than $6 billion since 1981.

Other floor moves included rejection of a move by Rep. Silvio O. Conte (R-Mass.) to kill the honey-support program. But then, on a 340-to-65 vote, the House agreed to an amendment by Rep. Barney Frank (D-Mass.) to limit individual honey-support loans to $250,000.

The chamber accepted an amendment by Rep. Robert E. Badham (R-Calif.) that struck from the bill a provision barring commercial use of an egg-breaking machine manufactured in Badham's district. The provision was sponsored by commercial egg-breakers who claimed the competing machine was a public health menace.