The resignation of Anne M. Burford as chief of the Environmental Protection Agency has left wildlife enthusiasts and ranchers confused about the fate of a potent poison once widely used to kill coyotes.

Last October, Burford said she would decide within 30 days whether the EPA would lift its ban on sodium fluoroacetate, commonly called Compound 1080. But she resigned before making a decision, leaving one of the more controversial chapters of her tenure unfinished.

Western ranchers had been pressuring the EPA for years to lift its ban on 1080, which the agency had ruled in 1972 was dangerous to humans and wildlife other than coyotes. In between her nomination and confirmation, Burford wrote ranchers' groups, urging them to challenge the 1080 ban. She later put her adviser, Denver attorney James W. Sanderson, in charge of arranging hearings on 1080 to see if the ban needed to be reconsidered.

In late 1981 Burford said those hearings had produced new evidence that justified re-examining the ban. She called for "expedited" hearings before an administrative law judge. A short time later, a California scientist accused Burford of falsifying his research about 1080 to help justify a new appraisal.

Last October, after six months of often-emotional hearings, Judge Spencer T. Nissen recommended that the EPA permit the use of 1080 under two carefully defined methods. Conservationists and the ranchers immediately appealed Nissen's order to Burford. She was prepared to announce her decision two months ago when she spoke to a national convention of woolgrowers in Oklahoma City, but at the last moment she dropped the decision from her speech, officials said.

Rep. James H. Scheuer (D-N.Y) announced yesterday that his House science subcommittee plans to hold hearings within the next few weeks to determine whether the EPA suppressed data about 1080.