Graves are a Waqf (endowment) for those who are buried in them

Praise be to Allah.

From what you say, it seems that the land you are asking about is a graveyard and that your farm borders it on the west. It is not part of your farm, since when you dug in it you found old graves containing bones, as you admit. It does not belong to you and it is not part of your farm, rather it is a Waqf (endowment) for those who are buried there, and it is not permissible for you or anyone else to take possession of it or use it for residential purposes, farming, construction, erecting tents or any other purpose. May Allaah bless our Prophet Muhammad and his family and companions.