decomposition is when a decomposer recycles / returns nutrients / nitrogen from dead organisms to the soil by eating those dead organisms & if something is returned to a place then that something is added to that place ->  decomposers add nitrogen to soil using decomposition  high quality / rich / good soil has a high number of nutrients / amount of nitrogen & fertile soil is high in quality ->  fertile soil is high in amount of nitrogen  decomposers add nitrogen to soil using decomposition & fertile soil is high in amount of nitrogen -> decomposers make fertile soil by adding nitrogen to soil