In a sandy soil, the antagonistic bacterial and fungal flora was analysed and their effectivity with respect to corn foot and stem rot was investigated. Measures that promoted total micro-flora in soil (organic fertilization) stimulated, in most cases, the antagonists as well. Different organic substances supported various types of antagonists. In soil with inhibited aeration the antagonists were reduced. A full effectivity of the antagonistic biological soil component presupposes the absence of host plants.