Workaround for disabling PvP on a Land Area you manage on Amethera:

1. In your Land Area Marker Settings, activate PvP and click Accept.
2. In your Land Area Marker Settings, disable PvP and click Accept.

After this, the Managed Land Area is no longer a PvP zone. However, you will have a yellow PvP symbol on the Radar since the surrounding area is still PvP.