Hi everyone, new to this forum and Maya.

I have worked with different programs and have some experience with textures and art. But cant seem to figure out how i can apply a texture to part of a material that already has a texture, on only a specific area.
Maybe the image will explain better..


Where there is grass, I want to add a new material.
Where there is sand, new material.
And same for the stone/rock texture..

So is there any utility or something that i can use where the above image can be used as an input for where to place other materials?
Thanks for your time.