Congressional conferees neared approval last night of a fiscal 1983 agriculture spending bill after rejecting new aid for dairy farmers, refusing to bar federal crop loans on erosion-prone land and hearing a bristling spat between their leaders over a research laboratory in Oregon.

The major remaining issue before the House-Senate conferees, still unresolved when they broke last night, involved funding levels for the special supplemental feeding program for women, infants and children (WIC).

Lobbyists for other commodities were active throughout the day. The always influential dairy advocates appeared to be working overtime, but they were turned aside on two major issues in the approximately $30 billion money bill, which will be roughly $6 billion over budget.

The House conferees adamantly refused to go along with Senate-passed language that would have required the inclusion of more milk solids in retail milk, a step that consumer advocates said could have raised prices by as much as 17 cents a gallon.

With that, the milk-solids language died but the dairymen almost pulled off a spectacular coup on the other issue. The conferees came within one vote of revoking a congressionally mandated fee against dairy farmers, which took effect Dec. 1, as a tool for reducing surplus milk production that costs the treasury about $2 billion per year.

The fee revocation was proposed by Rep. Jamie L. Whitten (D-Miss.), who wanted to make the levy contingent on the Department of Agriculture selling several billion pounds of government dairy surpluses. The administration has resisted pressure to dump U.S. milk on world markets for fear of trade retaliation.

Sen. Thad Cochran (R-Miss.), the conference chairman, resisted Whitten's proposal, contending that it constituted unlawful legislating on a spending bill. But his dairy-state colleagues balked and forced a roll-call vote on the Whitten proposal, which lost on a 4-to-4 tie.

Before the House-Senate conferees quit for the night, Sen. Mark O. Hatfield (R-Ore.), chairman of the Senate Appropriations Committee, had walked out when his House counterpart, Whitten, objected to three home-state projects that Hatfield showed up to promote personally.

In an unusual and pointed exchange, Whitten said his committee could offer no help until it got more information on the Oregon projects. Hatfield, taken aback, complained that in the past he had bowed to Whitten's wishes on his own pets and expected like treatment.

When it wasn't forthcoming, Hatfield left in a snit. Whitten later relented and assented to Hatfield's gift list, which included $750,000 for a federal forage seed laboratory at Oregon State University in Corvallis.