The Senate Agriculture Committee yesterday continued merrily along the big-spending path it has been following all week, diregarding President Reagan's budget limits as it voted generous new farm programs for the next four years. However, the chairman and many members of the panel said it would have to reconsider this week's decisions later to reduce their cost.

"We can't report out this monster," said Sen. Bob Dole of Kansas, second ranking Republican on the panel. Chairman Jesse Helms (R-N.C.) indicated he agreed. "All the senators [on the committee] know that we'll have to make adjustments" before reporting out a final bill, Helms said after yesterday's committee meeting.

Before he said that, Helms presided over votes which -- if allowed to stand -- would add perhaps $4 billion to the farm bill the Reagan administration has proposed for the next four years. Earlier in the week the committee approved other changes in the Reagan program that would raise its cost by another $2 billion or so.

Yesterday's votes authorized more generous programs to support feed grains, cotton and peanuts. Earlier the committee had gone beyond Reagan's proposals on dairy price supports and the wheat program, and added a new revolving fund to provide credits for exports of agricultural commodities.

Sen. Richard G. Lugar (R-Ind.), the most vocal Reagan loyalist on the committee, said yesterday his colleagues were playing "a very dangerous game," because "every senator who is trying to be an advocate for a specific farmer group is leading farmers to believe that [federal farm subsidies] will be much higher than will turn out to be the fact."

Lugar noted that many of the conservatives on the panel "who are cheering Ronald Reagan the other night" when he addressed Congress on the need for budgetary restraint are now supporting special-interest additions to the farm bill. "There may be a certain degree of cynicism" in this week's votes, Lugar said, in that members may be expecting to cut back these programs later. "But it'll be hard to get back to realism," he added.

Other members indicated they fully expected to reconsider the votes taken this week. "This is just a preliminary," said Howell Heflin (D-Ala.), who predicted that "we'll get out the knives" later. Helms said he thought Lugar's pessimism was unwarranted. It was typical procedure for the Agriculture Committee to run through the entire bill once before getting down to serious decisions.

Lobbyists for several agricultural interests said privately they feared the committee would have to go back and cut down its bill -- or face a presidential veto later, if something like its present bill wins full congressional approval.

On key votes yesterday and Wednesday on feed grain programs, the administration position was defeated by votes of 11 to 5. An attempt by Lugar to end all peanut acreage allocations and establish an essentially free market in peanuts was defeated 12 to 4.