In-vitro inhibition of mycelial growth of phytopathogenic fungi grown on potassium silicate amended media has been demonstrated. In the current study the respective effects on fungal
growth of changes in the pH of growth medium with increased concentrations of potassium silicate, and potassium silicate concentrations per se were investigated. To assess the effect of pH on mycelial growth, PDA was adjusted to pH’s
(10.3–11.7) similar to those associated with potassium silicate concentrations (20–80 ml.l-1 potassium silicate; 20.7% silicon dioxide) using KOH. Inhibition of mycelial growth was doserelated
with 100% inhibition at concentrations > 40 ml (pH
11.5) soluble potassium silicate per litre of agar. Inhibition of mycelial growth on KOH amended PDA ranged from 0–100% and the effect of pH on mycelial growth was inconsistent. Although soluble potassium silicate has a two-fold effect on fungal growth in vitro, the direct inhibitory effect clearly overrides the effect of pH.