How to make the road blend with the terrain's texture?

Hello. I'm creating a game like anno. I want my dirt road to blend with the terrain textures. I currently have grass and stone textures for my terrain. I added those textures using the terrainData.SetAlphamaps.

But I don't know how to do it when I have my road as a separate gameobject with mesh on it. I can do it using terrainData.SetAlphamaps but I'm wondering if I can blend a separate gameobject mesh's texture with the terrain texture?

Or is the SetAlphamaps the only way to do what I want?

Thank you