practises (on)

No. Most Americans would say it:
To prepare for her upcoming concert, Jennifer practices piano for two hours every day.

1. Jennifer practises (on) her piano for two hours every day to prepare for her upcoming concert.

2. Jennifer practises her piano for two hours every day to prepare for her upcoming concert.

It is needed in 1 to state the meaning that she uses her particular piano for the preparation. In 2. without 'on', the meaning is "her study of piano".