HAMBURG, West Germany (AP) _ West Germany gave Vladimir Horowitz the country's highest public service award Monday, a day after the 81-year-old pianist gave his first concert on German soil in 54 years.

Horowitz received the German Order of Merit in a ceremony at City Hall. On Sunday night, he stirred 1,800 spectators in the city's concert hall with a 2 1/2 -hour performance - receiving standing ovations before and after the performance.

The pianist attended the ceremony with his wife, Wanda, daughter of the late conductor Arturo Toscanini.

Horowitz listened to Mayor Klaus Dohnanyi's praise with a mixture of seriousness and amusement.

When Dohnanyi called him ''the greatest (musical) interpreter of our century'' and praised his concert as ''unbelievably beautiful,'' Horowitz beamed and said, ''Oooh 3/8''

When a television reporter asked him what the medal felt like hanging from his neck, Horowitz quipped, ''Heavy.''

Horowitz last month returned to the Soviet Union, his birthplace, for the first time since leaving 62 years ago.

Horowitz, now a U.S. citizen, last performed in Germany in 1932 in a six- concert series in Hamburg. His concert Sunday included works of Liszt, Schumann and Chopin.

His next concert is scheduled Sunday in West Berlin.