A senior Agriculture Department official confirmed yesterday that he helped two of his neighbors from California lobby with congressmen and officials against an administration decree that could force some large farmers, including himself, to sell part of their holdings.

Assistant Secretary of Agriculture Robert H. Meyer said he arranged the meetings here Sept. 15 with several congressmen and high officials at the Interior Department. But he denied that he had lobbied against the decree. He said he made clear that he was appearing only as a private citizen who stood to suffer financial losses because of it.

On Aug. 22, Interior Secretary Cecil D. Andrus issued the decree which, if implemented, will require large holders of land irrigated by federal projects in the West to sell of some of the acreage in five years.

The decree was based on a 1902 law which has been largely ignored in California and other parts of the West. It set strict ownership limits on this federally watered land - 160 acres each for a farmer, his wife and children.

The Interior Department acted after a federal appeals court panel in California ruled last month that the 1902 act applied to the Imperial Valley. Meyer said lawyers there have asked for a rehearing before the full court.

Meyer, his wife and five children own or are purchasing a total of 2,621 acres in the irrigated Imperial Valley. If the Interior Department goes through with its plan and is upheld in the courts, Meyer said, he could retain only 1,120 of those acres. The rest would have to be sold off to family farmers in a lottery.

Meyer said the Sept. 15 meetings were arranged on behalf of two Brawley, Calif., neighbors who also farm large irrigated acreages. He said he made clear that he was not there as a representative of the Department of Agriculture.

He said he excused himself for 45 minutes during the meeting at Interior because Agriculture Secretary Bob Bergland has instructed him earlier not to become involved in the controversy over administration policy toward the 1902 act. Meyer said Bergland told him there was no objection to his speaking about the problem on his own behalf.

Meyer contends that the federal government ruled repeatedly between 1933 and 1964 that the 1902 law did not apply to the Imperial Valley farmers because they had organized and financed their own irrigation canal before 1900. The farmers accepted federal water later, after assurances that they would not be subject to the 1902 act, Meyer said.

Yesterday Meyer met for 15 minutes with Bergland and other department officials, and said afterward that the secretary and other advisers felt the matter was a "tempest in a teapot."

"They told me I had acted judiciously and honestly," he said. However, a Bergland spokesman said the secretary had asked the department's legal counsel to take statements from the officials and congressman involved to determine if Meyer acted properly in his capacity as an assistant secretary.