I need to mix my topsoil with other material to increase the volume of soil. I have purchased topsoil from homedepot but despite it having some organic material it seems to have far too much clay to lay on its own on top of grass seed. As it dries it cracks and seems to have a brownish tint my original topsoil does not possess. Before I proceed with further seeding I would like to remove a batch of the existing topsoil and cut it with other materials. What would be my best bet for this task??