Abstract: A microorganism fertilizer which causes in the soil a phenomenal multiplication of fluorescent Pseudomonas that have a superior effect in preventing the common scab of potato. The microorganism fertilizer is obtained such that medium-temperature and high-temperature Actinomycetes are used as seed bacteria and cultured while being spread/agitated in an organic substance such as livestock manure, etc. in an isolated propagation bed. The thus obtained microorganism fertilizer can be used as a countermeasure against environmental pollution.