Incremental Refresh - PostgreSQL 9.2

I've got a Master server and a Test Server.

Master server has a 1.7 TB

Test server has a full copy from master - 1.7 TB.

The copy was made using pg_dump

I.E: /usr/pgsql-9.2/bin/pg_dump --exclude-table-data='junk.*' --format=custom geoop_live > bigdump.sql

Question:

Now that the test server has a full copy from master, how could I just do a incremental refreshing once a month?

Instead copying all the DB (1.7GB), just copy what has been changed?

Is that possible?

Cheers