The Agriculture Department has fired the highest-ranking black woman employe in its Extension Service, less than a week after she charged publicly that USDA was denying nutrition assistance to low-income minority families.

Edith P. Thomas, PhD, a nutritionist with a GM-14 ranking who earned $44,000 a year, was told by letter Monday that she was dismissed and ordered to remove her personal effects from her office at USDA by the close of business yesterday.

The dismissal notice was signed by Denzil Clegg, associate administrator of the Extension Service, who refused in an interview to discuss details of the Thomas case. He denied, however, that the firing was related to charges Thomas made in a news conference last week.

At her news conference, Thomas described a series of requests that black universities and U.S. territories had made to the Extension Service since 1980 for her technical aid in developing and carrying out nutrition and infant-care programs for poor families.

All requests were denied, Thomas said, although her supervisors put no limits on her dealing with predominantly white land-grant colleges and universities. She said that supervisors had told her they wanted the black schools to seek aid from the white schools rather than from USDA headquarters.

"There is only one logical conclusion that I can reach as to why my nutrition services have been denied to low-income, black and minority people despite this being a major function of my USDA job," she said. "A branch of the U.S. government, motivated by racism, has intentionally adopted a policy of keeping blacks and nonwhite minorities in a disadvantaged condition."

The Extension Service, combined with state universities, provides agricultural, horticultural and homemaking advice to the public.

The charges by Thomas, who has taught at Indiana University and the University of North Carolina, prompted a House Judiciary subcommittee chaired by Rep. Don Edwards (D-Calif.) to seek more details on the case from Agriculture Secretary Richard E. Lyng. She also drew support from the Rev. Jesse L. Jackson's National Rainbow Coalition.

Thomas said yesterday that she decided to go public with her charges after encountering resistance inside USDA and after repeated unsuccessful attempts to meet with Orville G. Bentley, assistant secretary for science and education who oversees Extension activities.

"I called his office several times and wrote to him and then sent a letter to his home. I thought if I could talk to him about services being denied to blacks, he would respond. But I have heard nothing," Thomas said.

Since joining USDA in 1980, Thomas has filed 10 formal complaints over racial slurs and discriminatory policies at Extension. Most of the complaints have been unresolved, although one is pending before the Equal Employment Opportunity Commission.

Extension's Clegg denied that civil-service rules had been circumvented in the dismissal. He said Thomas had been given proper notice, and that she had been offered "a great deal of accommodation."

The accommodation, Thomas said, included a $25,000 offer and a clean record if she would quit. She said she rejected the offer hoping for an approved transfer to an agency agreeable to hiring her, but it was denied.