Perennial runner-up Jay Sigel of Philadelphia lost the Middle Atlantic Amateur Golf Championship to fellow Pennslvanian Paul (Bucky) Erhardt on the second extra hole of a sudden-death playoff at windy Five Farms here today. Both golfers were tied at 295 after 72 holes of play.

Sigel, who was second to Gary Mankulish in 1975 and to Marty West in 1976, went to the semifinals of the U.S. Amateur championship this year and also won three matches against Britain playing on the Walker Cup team.

Today, he missed a three-foot putt on the tricky second green after making a remarkable recovery from the rough on his second shot to get just short of the green.

Erhardt was on the green in two, about 40 feet from the hole. Sigel made a fine chip shot, but was below the hole and on a sidehill for his three-footer. Erhardt lagged his approach putt four feet away and made the next one for his par. That put the pressure on Sigel, who surveyed his putt, backed off, and came back for the miss.

Erhardt, 37, who owns an auto parts company in Wilmington, Del., shot the best round of the tournament, a one-under-par 69, today. He started five strokes behind Sigel, who came in with a 74.

Dave King of Bethesda Country Club finished with par 70, but was six behind the leader. Nonetheless, KIng and Erhardt were the only golfers in four days of play to equal or better par.

Duke Delcher of Northfield, N.J., finished third at 298 while Jim Fitzgerald, of Potomac Valley, and Henri deLozier, of Columbia Country Club, tied at 299, King's 301 tied Buddy Marucci, former University of Maryland golfer.

Defending champion West, of Columbia Country Club, never could get it going today and closed with a 77 for 304.

Erhardt went three under par for the first eight holes. He birdied the short fourth hole from 10 feet; the sixth from 20 feet, and the eighth from five feet. He got his first bogey on the ninth after his tee shot landed in a trap.

He birdied the 10th from 10 feet but bogeyed the 11th when he put his drive in a creek. He also bogeyed the short 13th, but made up for that with a 15-foot birdie on the long 14th. He finished with a bogey on the 17th to come in with 36 after going out in 33.