Chemicals are so often equated with toxic and environmentally destructive products, and in many cases, this is true, but all material things are chemical. When a plant assimilates and uses an essential nutrient, it does not differentiate whether that nutrient came directly from a natural or synthetic source. The problem with synthetic fertilizers isn't that they contain toxic chemicals, per se. It is because they contain high levels of nutrients and they release those nutrients much too fast. The nitrogen derived from the ammonium sulfate, however, is identical to the nitrogen derived from the compost.
Soil amendments are products used to improve the properties of the soil.
It is important that the distinctions be kept in mind. Specifically, there have been, and perhaps continue to be, laws in different locations that have required packaged manures and composts could only be sold as soil amendments and not as fertilizers. This, however, was mostly the result of marketing. Manures and composts are both fertilizers and soil amendments. Composts and manures are in a class by themselves as first rate soil amendments and as nutrients for the plants and the soil organisms.