The House Agriculture Committee, under pressure to finish a farm bill before the August recess, voted last night to set up major new soil conservation programs after adopting a dairy surplus reduction plan that would pay farmers not to produce milk.

The conservation steps include denial of federal farm program aid to farmers who plow up highly erodible cropland or convert fragile wetlands to crop production. The bill also would create a 25 million-acre conservation reserve, which would pay farmers to remove erodible land from production.

Although both the conservation and dairy provisions would take federal farm policy in new directions, an underlying theme during debate was reduction of surplus production that generally has depressed farm prices and put farmers in the tightest economic straits since the Depression.

Supporters said the soil protection steps would reduce federal price-support costs while cutting excess production that hangs over grain markets. Dairy-change proponents said federal costs would drop by enticing dairy farmers into a farmer-financed program that pays them to cut milk output.

Although the administration opposes the milk surplus reduction scheme on philosophical grounds, supporters said that it would cut about $700 million from federal outlays of $1.7 billion to buy surplus milk, butter and cheese.

Before adopting the industry-written dairy plan, the committee overwhelmingly defeated a consumer-supported alternative, whose sponsor, Rep. James R. Olin (D-Va.), argued would save more federal money.

But Rep. Tony Coelho (D-Calif.), chairman of the dairy, poultry and livestock subcommittee, said the milk "diversion" plan was the only way to reduce surpluses without bankrupting thousands of farmers.

As the House committee was moving onto a fast track, with the first of what Chairman E (Kika) de la Garza (D-Tex.) said could be a string of more night meetings, its Senate counterpart finished work on the research section of its own farm legislation, continuing most federal research programs at spending levels slightly higher than current ones.

In one major move, the committee decided, with no debate, to back away from a proposal by Chairman Jesse Helms (R-N.C.) that called for sweeping changes in establishing federal research priorities.

The Helms language would have required the Agriculture Department to target its research to assist small and moderate-sized farming operations and directed a phase-out of research that benefited only large farmers.

Helms indicated that Sen. Pete Wilson (R-Calif.) had asked that the committee not order research to be redirected by statute. Rather, the final report on the bill would contain nonbinding language to that effect.