The gun deck is balsawood. The earth in front of the gabisons are fine wood filler, same as I now use on my bases, with a watered PVA glue and real dirt from the garden, the drit is also sprinkled on the gun deck it self. A small mortar is on the back of the deck, it's in for repares as it's wheels are on the table.
I'm quite happy with the gabisons, took quite a few layers of diffrent browns to get them ok.
I painted the mortar red simply to get some color.