Tuesday's elections ripped holes in the Republican membership of several House committees, and nearly decimated the farm-state Republicans on Agriculture.

Five of the 19 Agriculture Republicans appear to have lost, including three of the four most senior members from traditionally Republican farming areas.

The Democrats' apparent pickup of 26 seats in the House also means that the formula used to determine party ratios on all committees will be adjusted -- no one is sure by how much -- so that Republicans will have fewer members on each.

These ratios are often vital in the legislative process. On Agriculture, for instance, now 24 to 19 Democratic, Republicans this year and in 1981 were often able to link with conservative Democrats and provide the Reagan administration with important victories.

In sheer numbers, Armed Services will lose more sitting Republicans next year than any other House committee: seven. Three quit to run for the Senate and four others were defeated. Foreign Affairs and Government Operations each will lose six of their current Republicans.

The Democratic victories, combined with retirements, also mean that there apparently will be new ranking GOP members on four other committees: Banking, Finance and Urban Affairs; Judiciary; Public Works and Transportation; and Post Office and Civil Service. These, too, are vital leadership positions for the minority in scoring legislative points.

Banking will lose J. William Stanton (R-Ohio) from the ranking slot; Judiciary loses its No. 1 Republican, Robert McClory (Ill.), who retired, and No. 2, Tom Railsback (Ill.), a primary loser. Public Works will lose Don H. Clausen (Calif.), who was defeated Tuesday, and Edward J. Derwinski (Ill.), defeated in a primary, will be gone from Post Office.

Rep. William C. Wampler (R-Va.), his party's senior member on Agriculture, was an apparent loser in a tight race, but votes were being canvassed in his district yesterday. Wampler, not conceding defeat, said he would ask for a recount if the margin was 1,000 votes or less.

Next in line on Agriculture, Rep. Paul Findley (R-Ill.), was also an apparent loser by about 1,400 votes, but he was not conceding either. Aides said he was considering asking for a recount. Also out, ranking fourth on the committee, was Tom Hagedorn (R-Minn.).

Two other Republican losers from Agriculture were Reps. John L. Napier (S.C.) and Clint Roberts (S.D.), who was pitted against fellow committee member Thomas A. Daschle (D-S.D.) after their two districts were reformed into one. The fate of a sixth GOP member, Arlan Stangeland (Minn.), was not clear although he claimed a slim victory. His opponent is not conceding and has not decided if he will seek a recount.

Although the Republican hurt seemed deepest on Agriculture, most congressional and farm organization officials were wary of linking it entirely to farmer retaliation over the troubled state of the agricultural economy.

But Rep. E (Kika) de la Garza (D-Tex.), chairman of the Agriculture Committee, said he felt Tuesday's returns "seem to show that the severe economic problems affecting farmers had some effect at least in a number of races in rural areas."

"I think," he added, "the results mean the administration is going to have to be less rigid; the administration, I hope, will now be more willing to work with us in a bipartisan way to develop practical approaches to bring the farm economy back to health."