Abstract: A mushroom compost compacting system and method includes a roller assembly mounted to a compost receptacle to form a nip, and a web or conveyor to convey mushroom compost to the nip. Mushroom compost is compacted at the nip from an initial compost height to a final compost height. The roller assembly has a roller, a shaft, and fixtures coupled to each end of the shaft. The fixtures are adjustable to define the roller nip height. In one embodiment, the fixtures are mounted to sleeves that engage the sidewalls of the compost receptacle. In another embodiment, the ends of the fixtures are mounted to a support, which may be a joist or a separate channel extending under the floor portion of the compost receptacle, or which may be a post that forms support structure for the compost receptacle.