Ozonation was studied for inactivating Phytophthora sojae, a predominant soybean pathogen that causes root and stem rot, and pre-and post-emergence soybean damping-off. Typically, fungicides are used to treat soils to control the damage from P. sojae to soybean production. An environmentally friendly method of ozonation was studied for inactivating P. sojae, a model Phytophthora pathogen that affects a wide range of high-value crops. Assays of artificially inoculated soil samples with P. sojae were treated with different doses of gaseous ozone. This study showed that a dosage of 0.47 g.kg-1 O3 in the soil totally prevented root and stem-rot disease incidence by P. sojae. The findings of this research clearly indicate that ozonation is an efficient alternative to chemical fungicides in the inhibition of Phytophthora diseases in the soil, hence a balancing feedback loop reinforcing the soil system as natural capital.