Technical Abstract: The lack of success of biological control with soilborne diseases is primarily due to the introduction of the biological control organism into a sub-optimal environment. Indigenous soil microorganisms contribute to disease suppression in cropping systems by reducing and competing with pathogen populations limiting disease severity. Various communities of indigenous microorganisms in any particular soil have adapted to the specific environmental conditions. If the soil around the plant roots could be altered to favor the indigenous soil microorganisms relative to the plant pathogen, the survival and proliferation of indigenous soil microorganisms and thus effectiveness of biological control may be increased. We used wood chip-polyacrylamide (PAM) cores to alter the soil environment in a greenhouse study to favor indigenous soil microorganisms in vegetable and manure compost to reduce Verticillium dahliae infection of potato plants. Potato plants gorwing in soils amended with vegetable compost-wood chip-PAM cores had substantially lower visible and isolation Verticillium dahliae infection rates than control soils and soils with dairy or vegetable compost alone. Soils with wood chip-PAM cores and soils with wood chip-PAM-vegetable compost had higher microbial biomass/Verticillium dahliae biomass (MB/VB) ratios in soil than control soils or soils amended with compost. MB/VB ratios in wood chip-PAM cores and wood chip-PAM-vegetable compost were higher than in wood chip-PAM-dairy compost cores. Verticillium dahliae infection negatively correlated curvinlinearly with the MB/VB ratio (r**2=0.76).