The soil replica plating technique was used to evaluate the influence of clay
minerals and pH on antagonistic interactions between fungi and bacteria in soil In general, the antagonistic activity of bacteria towards filamentous fungi was
greater in soil than on agar. The spread of Aspergillus niger through soil was
inhibited by Serratia marcescens when the organisms were inoculated into
separate sites in soil, and this antagonistic effect was maintained when the soil
was amended with 3, 6, 9, or 12% (vol/vol) montmorillonite, whereas the addition
of kaolinite at a concentration of 3% reduced the antagonism and at 6, 9, or 12%
totally eliminated it.