It is an apocope (in Italian troncamento or apocope), a usual phenomenon in which one or more final letters of a word are omitted, usually for metrical or general euphonic reasons, not specific of a particular grammatical person or number (but with its own empirical rules).
Some troncamenti are now fixed (think about buon giorno rather than *buono giorno, un uomo rather than *uno uomo, dottor Rossi vs.*dottore Rossi). Others are optional, and left to one's sense of the language and the different emphasis to be given to a sentence (ti vuole bene as well as ti vuol bene).
In Italian you can read more about it in Treccani Enciclopedia dell'Italiano's article about troncamento.