a field experiment conducted with the irrigated rice cultivar brs formoso, to assess the efficiency of calcinated serpentinite as a silicon source on grain yield was utilized to study its effect on leaf blast severity and tissue sugar levels. the treatments consisted of five rates of calcinated serpentinite (0, 2, 4, 6, 8 mg.ha-1) incorporated into the soil prior to planting. the leaf blast severity was reduced at the rate of 2.96% per ton of calcinated serpentinite. the total tissue sugar content decreased significantly as the rates of serpentinite applied increased (r2 = 0.83). the relationship between the tissue sugar content and leaf blast severity was linear and positive (r2 = 0.81). the decrease in leaf blast severity with increased rates of calcinated serpentinite was also linear (r2= 0.96) and can be ascribed to reduced sugar level.