John D. Schapiro, president of Laurel Race Course, announced yesterday that he has signed a joint venture agreement with Pimlico Race Course in the acquisition of Bowie Race Course, the state's other mile thoroughbred track. Industry sources say the move will lead to attempts to eliminate Bowie as a race track as early as 1985.

The formal settlement for the sale of Bowie is set for Thursday, Schapiro said.

The purchase price for Bowie is $12 million, including debt assumption. Schapiro said Pimlico and Laurel each would own 50 percent of the joint venture. "For the time being, we intend to pursue the same plan as outlined by Pimlico--to operate Bowie . . . and see what happens," Schapiro said yesterday from his Baltimore office. At the time Pimlico signed the papers to buy Bowie, Pimlico management said it had no immediate plans to transfer any of Bowie's 112 racing dates from the Prince George's County track.

Sources familiar with tax laws say any announcement of plans for a race track consolidation at this time could adversely affect the tracks' tax benefits in the Bowie purchase.

But racing industry sources said yesterday that the most efficient way for thoroughbred racing to operate and improve in Maryland is consolidation to two tracks, with each facility being renovated. In order for this to happen, the Maryland legislature would have to pass bills allowing a shift of racing days from one track to another and a reduction of the state tax on parimutuel wagering to be used for track improvements. The current parimutuel tax on thoroughbred racing is 4.09 percent.

A consolidation could lead to Sunday and night thoroughbred racing at the mile tracks, the sources said.

Del. Paul Weisengoff (D-Balt. City), chairman of the racing subcommittee of the House Ways and Means Committee, said yesterday that attempts at a complete consolidation could be a complex political issue, but that the legislature probably would look favorably at a reduction in the state pari-mutuel tax, because of the investment by Pimlico and Laurel in buying Bowie.

He said representatives of the two tracks have not indicated any specific legislation they would seek when the Maryland legislature reconvenes in January. But Weisengoff speculated that there may be an attempt to get legislation to move 52 of Bowie's 112 days .

Those days would include the 36 racing days Bowie bought from now defunct Marlboro and 16 days of summer racing dates owned by the state. Maryland currently has 306 days of thoroughbred racing. Besides Bowie's 112 days, there currently are 76 days each at Pimlico and Laurel and 42 at Timonium, the state's lone half-mile track.

A plan that would have given the mile tracks 32 of Timonium's days was rejected recently by the track's board of directors. Gov. Harry Hughes has asked Timonium to close down, a move that would enable to state to have year-around racing at the mile tracks.

There also is a report that Hughes is considering the establishment of a secretary of sports, who would oversee horse racing and boxing, and that whoever is selected for the cabinet-level position would act as the state's "racing czar," as one source put it. Racing now is handled by the Department of Licensing and Regulation.