Rice-based irrigated lowlands are the major cropping system in north of Iran. This experiment was carried out in split plot in basis of randomized complete block design with three replications at north of Iran in 2010. Main plot was nitrogen rates including (0, 50, 100 and 150 kg N ha-1) applied as urea and sub plot was silicon rates (0, 300 and 600 kg ha-1) applied as calcium silicate. Results showed that minimum of the plant height, flag leaf length, fourth inter-node bending moment and grain yield (4350 kg ha-1) were obtained at N0, as well as the maximum of the plant height, panicle length, flag leaf length, third inter-node length were observed at N100 and N150, respectively. But the highest of bending moment obtained for fourth inter-node and maximum grain yield (6063 kg ha-1) was observed in N150. Treatment Si600 had increased significantly over control in plant height, stem length, panicle length, third inter-node length, third inter-node bending moment, cellulose, hemi-cellulose and lignin in relation to 7.76, 9.91, 30.18, 31.03, 18.71, 7.60, 34.50 and 26.26 %, respectively. Therefore treatment with N150 and Si600 had shown best results for agronomical indices and grain yield.
