The case of Everett G. (Bud) Rank Jr., who is a partner in a California farm enrolled in the payment-in-kind (PIK) program that he administers here, still is under study by Agriculture Department ethics officials.

Records of the Agricultural Stabilization and Conservation Service (ASCS), which Rank has headed since his appointment in March, 1981, show that the farm in Fresno County is scheduled to receive 1.3 million pounds of free cotton, worth more than $1 million, through the PIK program.

The program was set up earlier this year to give farmers federal surpluses in return for not planting corn, wheat, rice and cotton. By curbing production, the administration hopes to reduce surpluses and bolster sagging farm prices.

Rank said last week that he learned only recently that his partners had enrolled the farm in PIK. He said he believed there was no conflict, since he played no role in the farm's operations, and he said he would receive no benefit from the farm's participation in the program.

Michael W. Kelly, who reviews ethical questions for the USDA's general counsel, said that a letter Rank sent last week to Sen. Jesse Helms (R-N.C.), chairman of the Senate Agriculture Committee, helped clarify the situation. But, he added, "It is fair to say we are going to pursue this . . . . The department will consider if further steps are required if there is another year of the PIK program."

Also looking at the case, but awaiting USDA's findings, is the Office of Government Ethics at the Office of Personnel Management.

Secretary John R. Block, for one, apparently has no problems with Rank's situation, although he pledged to keep his own farming operations out of federal support programs. Block indicated to reporters last week that the flap over Rank puzzled him. An aim of PIK, he said, had been to enroll as many farmers as possible and now that Rank's farm is in PIK "he's on the pan . . . . You can't win."

On another front, Rank has been admonished by Undersecretary Daniel G. Amstutz and has been ordered to cough up $588.85 to repay the government for the illegal use of a government car by himself, his family and a friend, William McFarlane, who heads the Cinco Farms partnership that includes Rank. The amount was calculated to include 25 hours of overtime for a driver and $480 to cover mileage.

A USDA inspector general's investigation, touched off by an anonymous tipster, found that Rank had used the official car a number of times for personal business, including rides to and from airports and trips to social events. McFarlane, also a member of the board of the Federal Crop Insurance Corp., was given a free ride from Dulles International Airport to Rank's home in March, 1982, the probe found.

In a sworn statement, Rank said he was sure he could justify the ride for McFarlane "but would prefer not to have to." Rank said McFarlane usually stays with him when he visits Washington. Rank conceded that some of the questionable uses of the federal car did occur, but he maintained that he had "never received an official briefing per se on the proper use of the government vehicle and chauffeur." * * *

FAIR FARE AND SUCH . . . Just off his much-publicized, week-long trial of the diet recommended for food-stamp recipients, Secretary Block will lead a one-mile celebrity run at 10:30 a.m. Thursday to kick off a USDA food-and-fitness campaign. Departmental wags are wondering if he'll have the stamina to finish after a week of trying to feed a family of four on food costing $58.

Among the runners joining Block will be former Washington Redskins coach George Allen, who is chairman of the President's Council on Physical Fitness. A centerpiece of the USDA's nationwide campaign will be a fair, through Saturday on the Mall outside USDA headquarters, featuring farm animals and equipment, health screening, nutrition programs and athletic events.

On the nutrition front, Block's wife, Sue, is scheduled to appear at noon today at what is billed as the first "Salad Bowl," at 14th and Taylor streets NW, to show off the D.C. Recreation Department's Washington Youth Gardens project, which teaches vegetable gardening to more than 2,000 inner-city youngsters.