For example, instant coffee powder, when heavily doused with hairspray, looks like thick mud. Different types of chillie and curry powders give a great dry soil look. Peterselie looks just like leaf mould. Coarse chillie flakes look like autumn leaves.
The base I've shown was for a 1/16 fig, but by grinding the spices finer they can be used for smaller scales. I had added some twigs and dried moss, but I've removed most of it, along with the the fig so that you can see the ground better.
Word of warning: your workroom's going to smell like an Indian curry shop for a while, but the smell of the spices soon fade, especially when you use hair spray to set it. I didn't use glue at all, just several layers of hairspray and spices so that the texture is preserved.
The second pic is with a flash so the colours are a bit off but its sharper.
I've used this technique on most of my fig bases as it's a lot cheaper and looks ok. The third pic's an example. Hope you can see what I mean. I'm also using it for my July FOTM entry which I will submit soon.