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Effect of Nitrogen and Silicon were field studied on rice blast disease and yield in Hassan-Saraie cultivar for two years. Rates of Nitrogen were 0,
60, 90 and 120 kglha, while 0,300, 600 and 900kg/ha were the rates for slag that was the source for silicon ( SiO2 34%). For evaluation, number of leaf
blast spots on tOO-tillers at the stem elongation stage, percentage of panicle blast at the mature grain stage, number of silicified cells in 20 samples of flag leaves, as well as yield, were determined and statistically analysed. The results
showed that the application of nitrogen increased the blast disease and rice yield, but it wasn't effective regarding the silicified cells. Silicon ( slag obtained
from steel mill ) didn't indicate any decreasing of blast disease or increasing of rice yield, but it increased silicified cells when applied at 900kglha in the second year, the increase being significantly different from control at 5% level
by DMRT.