Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Natural material: Ammonia is often the side effect of organic matter in the soil. This is especially the case with using garden soil with some compost as an aquarium substrate. The leaves, microorganisms, worm poop, and other things in the soil had some protein in them when they were alive, and this protein decomposes once the organism is dead. The nitrogen in protein becomes ammonia.
If a material is designed, made for garden or aquarium use, and has some fertilizer added, then the ammonia might have been directly added (especially for garden use) or it might be the effect of some other material like urea breaking down.