These aren't the best of times for some of the people at the Agriculture Department.

Wayne Mayfield, a Republican appointee who has headed the Texas operations of the Agricultural Stabilization and Conservation Service since 1981, began a 30-day suspension without pay this week after an investigation found him guilty of misconduct.

ASCS officials here said they were unsure about details of the case, but Roy Cozart, an assistant deputy administrator, said he understood that it involved misuse of a government vehicle. But, he added, "I support the man as being one of the top state directors in the nation as far as his knowledge of programs and management ability."

Other USDA executives disclaimed knowledge of the Mayfield case or refused to discuss details.

In neighboring Oklahoma, the Kingfisher County supervisor of the Farmers Home Administration (FmHA), Roy D. Brake, pleaded guilty this week to one count of embezzlement involving more than $1 million in USDA farm loans.

USDA officials said that Brake embezzled about $958,000 from at least eight loans made under his supervision and that he had used part of the money to buy a farm, several motor vehicles and a turbojet helicopter. Some of the money also financed a helicopter company owned by Brake and an associate.

Brake faces penalties of up to 10 years in prison and $10,000 in fines.

In Alaska, two U.S. Forest Service officials have been suspended as a result of firing a temporary employe who complained about their personnel policies in a letter to the editor of a local newspaper.

The USDA decided to suspend supervisors Robert Lynn and Joseph Chiarella for 30 and 14 days, respectively, after K. William O'Connor, special counsel of the Merit Systems Protection Board, filed charges alleging that they had mistreated Istvan Toth, who had written to the paper.

Lynn and Chiarella contended that Toth's letter, questioning Forest Service policy that sought to give an $11.96-an-hour laborer's job to the least educated and least experienced candidate, held the agency up to public scorn. They fired him summarily. After O'Connor charged that Toth's free-speech rights and federal personnel rules had been violated, the agency gave Toth back pay and restored his rights to reemployment. FAT IN THE FIRE . . .

Baseball season means hot dogs. But if you're curious about the amount of fatty calories in those ball park wieners (as well as others), you'll just have to remain curious. USDA has rejected a petition seeking mandatory labeling of fat content in processed meat products.

The petition was filed in November by Public Voice for Food and Health Policy. Support quickly came from more than a dozen other public health and citizen organizations that advise Americans to reduce their fat intake.

Public Voice wanted labels to disclose the number of grams of fat per serving of meat and the percentage of calories contained in the fat. Ellen Haas, head of Public Voice, argued that the labeling was justified by growing evidence linking fat to health disorders.

In its rejection, USDA said that the meat industry is working to provide more information and that Public Voice's approach would "mislead" consumers. The department said it agreed that the public needed more nutrition information, but that it preferred to let "market forces" inform meat eaters.

"It's doublethink," said Haas. "They recognize the problem but are not willing to do anything about it. This Department of Agriculture is no friend to the consumer or of the nutritional needs of the public." LAND HO! . . .

New data from USDA continue to show that, contrary to popular perceptions, foreigners still own only about 1 percent of American farmland. Foreign holdings increased by 300,000 acres in the past fiscal year to about 14 million acres, with slightly more than half of that in forest land.

Heavily forested Maine had the highest foreign ownership of private agricultural land -- 2.9 million acres, or 15.5 percent. Other leading states were Georgia, with 1.1 million acres; Texas, 972,000 acres; California, 906,000. Virginia had 134,000 acres and Maryland, 47,000, in foreign hands.