The Maryland Racing Commission decided yesterday to alternate the 48 summer thoroughbred racing dates between Bowie and Laurel, provided Bowie builds a turf course and Laurel airconditions its clubhouse.

The commission, meeting at Bowie, awarded the state's coveted spring dates (March 15-May 24) to Pimlico, the largest producer of revenue among the four flat tracks.

The commission said that for Laurel to get the 1981 summer dates, it would have to comply with the air-conditioning edict. Laurel President John D. Schapiro estimate the cost of such installation at $1.5 million.

The commission recommended that Bowie experiment with Sunday racing beginning the week of Jan. 21. Tracks usually follow such "recommendations." b

Bowie will have until 1982 to install a turf course inside its mile dirt track.

The 1980 Maryland racing calendar:

Bowie -- Jan. 1 through March 14, 60 days, four dark days.

Pimlico -- March 15 through May 24, 60 days, one dark day.

Bowie (summer) -- May 26 through July 19, 48 days, no dark days.

Timonium -- July 21 through Sept. 6, 42 days, no dark days.

Bowie (Marlboro meeting) -- Sept. 8 through Oct. 18, 36 days, no dark days.

Laurel -- Oct. 20 through Dec. 31, 60 days, three dark days.